interference and point-of-care testing devices€¦ · interference and point-of-care testing...
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Nam K. Tran, PhD, HCLD, (ABB), FACB Associate Clinical Professor Director of Clinical Chemistry, Special Chemistry/Toxicology and POCT
Interference and Point-of-Care Testing Devices
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Learning Objectives • Identify common interferences affecting POC
testing • Describe cases where interfering substances
affected patient care. • Describe solutions to mitigate the impact of
interfering substances on POC testing.
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POCT Device Formats Definition: POCT is defined as testing at or near the site of patient care
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POCT Device Formats Examples: • Disposable
• Handheld
• Portable
• Transportable
• Benchtop
• Monitoring
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POCT Device Formats Examples: • Disposable
• Handheld
• Portable
• Transportable
• Benchtop
• Monitoring
Being FDA approved as a POCT device does not mean it is not susceptible to interfering substances!!!
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Pre-Analytical
Total Testing Process: Lab testing occurs over three critical phases:
Total Testing Process: Difference Phases
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Pre-Analytical Analytical
Total Testing Process: Difference Phases Total Testing Process: Lab testing occurs over three critical phases:
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Pre-Analytical Analytical Post-Analytical
Total Testing Process: Difference Phases Total Testing Process: Lab testing occurs over three critical phases:
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Pre-Analytical Analytical Post-Analytical TREATMENT
Total Testing Process: Difference Phases Total Testing Process: Lab testing occurs over three critical phases:
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Pre-Analytical Analytical Post-Analytical TREATMENT
Errors in the Pre-Analytical Phase: Most frequent source of errors (up to 70%). Incorrect
Patient preparation Sample collection Transportation Accessioning Processing
Total Testing Process: Sources of Error C
ompo
nent
s
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Pre-Analytical Analytical Post-Analytical TREATMENT
Errors in the Pre-Analytical Phase: Most frequent source of errors (up to 70%). Incorrect
Total Testing Process: Sources of Error
Patient preparation Sample collection Transportation Accessioning Processing
Incorrect patient ID Mislabeling of specimens Hemolysis Wrong specimen type Improper specimen collection Interfering substances
Com
pone
nts
Sour
ces
of E
rror
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Pre-Analytical Analytical Post-Analytical TREATMENT
Testing
Total Testing Process: Sources of Error
Patient preparation Sample collection Transportation Accessioning Processing
Incorrect patient ID Mislabeling of specimens Hemolysis Wrong specimen type Improper specimen collection Interfering substances
Errors in the Analytical Phase: Infrequent in laboratory tests, however may be higher in POCT due to non-lab trained personnel operating devices.
Com
pone
nts
Sour
ces
of E
rror
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Pre-Analytical Analytical Post-Analytical TREATMENT
Testing
Total Testing Process: Sources of Error
Patient preparation Sample collection Transportation Accessioning Processing
Incorrect patient ID Mislabeling of specimens Hemolysis Wrong specimen type Improper specimen collection Interfering substances
QC/calibration Operator error Bad reagents
Errors in the Analytical Phase: Infrequent in laboratory tests, however may be higher in POCT due to non-lab trained personnel operating devices.
Com
pone
nts
Sour
ces
of E
rror
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Pre-Analytical Analytical Post-Analytical TREATMENT
Results interpretation Entry to LIS/EMR Contacting providers Sample archiving
Total Testing Process: Sources of Error
Testing
Patient preparation Sample collection Transportation Accessioning Processing
Incorrect patient ID Mislabeling of specimens Hemolysis Wrong specimen type Improper specimen collection Interfering substances
QC/calibration Operator error Bad reagents
Errors in the Post-Analytical Phase: Second most common among laboratory-based results.
Com
pone
nts
Sour
ces
of E
rror
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Pre-Analytical Analytical Post-Analytical TREATMENT
Results interpretation Entry to LIS/EMR Contacting providers Sample archiving
Total Testing Process: Sources of Error
Testing
Patient preparation Sample collection Transportation Accessioning Processing
Incorrect patient ID Mislabeling of specimens Hemolysis Wrong specimen type Improper specimen collection Interfering substances
QC/calibration Operator error Bad reagents
Misinterpretation of results IT problems
Errors in the Post-Analytical Phase: Second most common among laboratory-based results.
Com
pone
nts
Sour
ces
of E
rror
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Pre-Analytical Analytical Post-Analytical TREATMENT
Results interpretation Entry to LIS/EMR Contacting providers Sample archiving
Total Testing Process: Sources of Error
Testing
Patient preparation Sample collection Transportation Accessioning Processing
Incorrect patient ID Mislabeling of specimens Hemolysis Wrong specimen type Improper specimen collection Interfering substances
QC/calibration Operator error Bad reagents
Misinterpretation of results IT problems
Errors in the Post-Analytical Phase: Second most common among laboratory-based results.
Com
pone
nts
Sour
ces
of E
rror
What is the significance of testing error in POCT?
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Glucose Meter Paradigm to Highlight the Role of Testing Errors
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Glucose Meter Paradigm to Highlight the Role of Testing Errors
>12,000 glucose meter errors are reported to the FDA each year – highest number of adverse events for any in vitro diagnostic device.
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Glucose Meter Paradigm to Highlight the Role of Testing Errors
>12,000 glucose meter errors are reported to the FDA each year – highest number of adverse events for any in vitro diagnostic device.
12,672 serious injuries reported from 2004-2008 to the FDA.
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Glucose Meter Paradigm to Highlight the Role of Testing Errors
>12,000 glucose meter errors are reported to the FDA each year – highest number of adverse events for any in vitro diagnostic device.
12,672 serious injuries reported from 2004-2008 to the FDA. Most of these reported errors are due to erroneous results from interfering substances and operator error.
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Glucose Meter Paradigm to Highlight the Role of Testing Errors
>12,000 glucose meter errors are reported to the FDA each year – highest number of adverse events for any in vitro diagnostic device.
12,672 serious injuries reported from 2004-2008 to the FDA. Most of these reported errors are due to erroneous results from interfering substances and operator error.
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Glucose Meter Paradigm to Highlight the Role of Testing Errors
>12,000 glucose meter errors are reported to the FDA each year – highest number of adverse events for any in vitro diagnostic device.
12,672 serious injuries reported from 2004-2008 to the FDA. Most of these reported errors are due to erroneous results from interfering substances and operator error.
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Common Confounding Factors for Glucose Meters
Anemia and polycythemia causes falsely high or falsely low results respectively.
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-80
-60
-40
-20
0
20
40
60
0 10 20 30 40 50 60 70
BIA
S (m
g/dL
)
Hematocrit (%)
y = -0.9465x + 30.951 R² = 0.4171
Hematocrit Effects on BGMS Measurements
Note: Bias = BGMS – Plasma Glucose
Sample Size: 60 Hematocrit Range: 19 - 60% Glucose Range: 90 - 296 mg/dL
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Common Confounding Factors for Glucose Meters
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Common Confounding Factors for Glucose Meters
Oxidizing and reducing substances interfere with electrochemical sensors causing falsely high or low results.
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Drug Interferents (Oxidizing Substances)
Tang Z, et al. Am J Clin Pathol 2000;113:75-86
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The role of drug interferences in critical care BGMS accuracy
Tran NK, et al. J Burn Care Res
2014;35:72-79
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50
100
150
200
250
300
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36
Time Following Admission (Hours)
Blo
od G
luco
se (m
g/dL
)
Started Ascorbic Acid (66 mg/kg/hr) Stopped Ascorbic Acid
BGMS B*** History: Patient is a 21 y/o
woman with 90% TBSA burns from MVA.
CASE EXAMPLE: ASCORBIC ACID INTERFERENCE
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50
100
150
200
250
300
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36
Time Following Admission (Hours)
Blo
od G
luco
se (m
g/dL
)
Stopped Ascorbic Acid
BGMS B PLASMA GLUCOSE (Lab)
Started Ascorbic Acid (66 mg/kg/hr)
CASE EXAMPLE: ASCORBIC ACID INTERFERENCE
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50
100
150
200
250
300
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36
Time Following Admission (Hours)
Blo
od G
luco
se (m
g/dL
)
Stopped Ascorbic Acid
BGMS A BGMS B*** PLASMA GLUCOSE (Lab)
Started Ascorbic Acid (66 mg/kg/hr)
CASE EXAMPLE: ASCORBIC ACID INTERFERENCE
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Common Confounding Factors for Glucose Meters
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Common Confounding Factors for Glucose Meters
Specimen temp alters biosensor enzyme kinetics. Hypotension/shock affect capillary specimens.
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Common Confounding Factors for Glucose Meters
Some glucose meters cannot differentiate between certain non-glucose sugars (e.g., maltose, galactose)
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Non-Glucose Sugar Interferences
• Icodextrin is a dialysis drug. It is metabolized by the body to maltose. In some glucose biosensors, maltose is indistinguishable from glucose.
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FDA MAUDE Database website: http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfmaude/ search.cfm, Accessed on August 20, 2014
BGMS A BGMS B BGMS C
Timeframe 1997-14 2013-14 2007-11
Adverse Events (Deaths)
28 (13) 5 (0) 0 (0)
Erroneous Results 557 168 15
Non-Clinical Event 387 59 21
TOTAL 1094 232 36
Maltose Related Deaths
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Similar sensor designs so susceptible to similar interferences (will vary based on manufacturer).
CGM based on interstitial fluid measurements and not plasma or whole blood.
Potential for many other sources of interferences.
CGM does not fall under CLIA and most devices compared against obsolete or poor reference methods such as the YSI.
Use WITH caution!
Continuous Glucose Monitors?
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INTERFERENCES IN WHOLE BLOOD ANALYSIS
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INTERFERENCES IN WHOLE BLOOD ANALYSIS
Air Contamination
Delayed Testing
Hemolysis
Hemodilution/Hemoconcentration
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INTERFERENCES IN WHOLE BLOOD ANALYSIS
Air Contamination
Delayed Testing
Hemodilution/Hemoconcentration
Hemolysis
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Air Contamination of Blood Specimens
Background: Anesthesia reports “impossible venous blood gas values” in one patient where end tidal CO2 was greater than the venous blood gas (VBG).
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Air Contamination of Blood Specimens
Background: Anesthesia reports “impossible venous blood gas values” in one patient where end tidal CO2 was greater than the venous blood gas (VBG). • POC Venous Blood Gas: pH = 7.54, pCO2 = 17.5, pO2 = 168.5
• POC VBG#2: pH = 7.56, pCO2 = 12.7, pO2 = 165.9
• End tidal CO2 = 28
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Air Contamination of Blood Specimens
Background: Anesthesia reports “impossible venous blood gas values” in one patient where end tidal CO2 was greater than the venous blood gas (VBG). • POC Venous Blood Gas: pH = 7.54, pCO2 = 17.5, pO2 = 168.5
• POC VBG#2: pH = 7.56, pCO2 = 12.7, pO2 = 165.9
• End tidal CO2 = 28
• Lab Venous Blood Gas: pH 7.54, pCO2 = 19.2, pO2 = 161.5
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Air Contamination of Blood Specimens
Blood Gas Laboratory identified “air bubbles” in syringe
Background: Anesthesia reports “impossible venous blood gas values” in one patient where end tidal CO2 was greater than the venous blood gas (VBG). • POC Venous Blood Gas: pH = 7.54, pCO2 = 17.5, pO2 = 168.5
• POC VBG#2: pH = 7.56, pCO2 = 12.7, pO2 = 165.9
• End tidal CO2 = 28
• Lab Venous Blood Gas: pH 7.54, pCO2 = 19.2, pO2 = 161.5
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Air Contamination of Blood Specimens
Background: Anesthesia reports “impossible venous blood gas values” in one patient where end tidal CO2 was greater than the venous blood gas (VBG). • POC Venous Blood Gas: pH = 7.54, pCO2 = 17.5, pO2 = 168.5
• POC VBG#2: pH = 7.56, pCO2 = 12.7, pO2 = 165.9
• End tidal CO2 = 28
• Lab Venous Blood Gas: pH 7.54, pCO2 = 19.2, pO2 = 161.5
• Air bubbles can quickly (<5 mins) cause the specimen to
equilibrate atmospheric air (1 atm = 760 mmHg = 0.21 x 760 = 150 mmHg for pO2!!!)
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INTERFERENCES IN BLOOD GAS ANALYSIS
Air Contamination
Delayed Testing
Hemolysis
Hemodilution/Hemoconcentration
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Pre-Analytical • Transportation delays Analysis should be performed within 20 to
30 minutes—Faster is better!
Specimen Processing Delays and Lactate
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Pre-Analytical • Transportation delays
Seymour CW, et al. BMC Research Notes 2011;4:169
Specimen Processing Delays and Lactate
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Pre-Analytical • Transportation delays • Inadequate inhibition of
glycolysis
If delays are expected, using a grey top tube may be appropriate, however it may take up to 15 minutes to achieve inhibition!
Specimen Processing Delays and Lactate
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Pre-Analytical • Transportation delays • Inadequate inhibition of
glycolysis
Astles R, et al. Clin Chem 1994;404:1327
Specimen Processing Delays and Lactate
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Pre-Analytical • Transportation delays • Inadequate inhibition of
glycolysis
If delays are expected, using a grey top tube may be appropriate, however it may take up to 15 minutes to achieve inhibition!
Astles R, et al. Clin Chem 1994;404:1327
Specimen Processing Delays and Lactate
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Pre-Analytical • Transportation delays • Inadequate inhibition of
glycolysis • Specimens not placed on ice
False elevations of lactate could be mitigated by placing samples on ice. Iced samples exhibit similar results to those tested immediately at up to 6 hours.
Specimen Processing Delays and Lactate
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Pre-Analytical • Transportation delays • Inadequate inhibition of
glycolysis • Specimens not placed on ice
Seymour CW, et al. BMC Research Notes 2011;4:169
Specimen Processing Delays and Lactate
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INTERFERENCES IN WHOLE BLOOD ANALYSIS
Air Contamination
Delayed Testing
Hemolysis
Hemodilution/Hemoconcentration
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• Spectrophotometric (Non-Cyanohemoglobin)
Contemporary Hemoglobinometric Techniques
• Measurement of hemoglobin is based on the absorption spectra
• Oxy- and deoxyhemoglobin exhibit
different absorption in the red to IR wavelengths.
• Measurement based on Beer’s Law (A = elc).
• Some methods require lysis and reacting with non-cyanide-based reagents.
Abso
rban
ce
HHb O2Hb COHb MetHb
Prism
White light
500 550 600 650 700 nm
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Conductance (Impendance)
Contemporary Hemoglobinometric Techniques
Electrode
VS.
• Red blood cell membranes are not conductive.
High Resistance Low Resistance
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Conductance (Impendance)
Contemporary Hemoglobinometric Techniques
Electrode
VS.
Hematocrit (%)
Res
ista
nce
(Ω)
• Red blood cell membranes are not conductive.
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Conductance (Impendance)
Contemporary Hemoglobinometric Techniques
Electrode
VS.
• Red blood cell membranes are not conductive.
• The number of red blood cells is proportional to the change in conductance and conforms to Ohm’s Law (V = IR)
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Conductance (Impendance)
Contemporary Hemoglobinometric Techniques
Electrode
VS.
• Red blood cell membranes are not conductive.
• The number of red blood cells is proportional to the change in conductance and conforms to Ohm’s Law (V = IR)
• Conductance-based methods measure hematocrit. The hematocrit can then be used to calculate hemoglobin based on a conversion factor (estimated hemoglobin = hematocrit / 3.4)*
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Conductance (Impendance)
Contemporary Hemoglobinometric Techniques
Electrode
VS.
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Case Study 2: Hemoconcentration
Background: Patient with suspected Ebola Virus symptoms admitted for evaluation. Isolation protocols were in effect.
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Case Study 2: Hemoconcentration
Background: Patient with suspected Ebola Virus symptoms admitted for evaluation. Isolation protocols were in effect.
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Case Study 2: Hemoconcentration
Background: Patient with suspected Ebola Virus symptoms admitted for evaluation. Isolation protocols were in effect. A handheld blood gas chemistry analyzer served as the primary chemistry analyzer. 0853 hrs – Specimens collected for chemistry and CBC testing.
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Case Study 2: Hemoconcentration
Background: Patient with suspected Ebola Virus symptoms admitted for evaluation. Isolation protocols were in effect. A handheld blood gas chemistry analyzer served as the primary chemistry analyzer. 0853 hrs – Specimens collected for chemistry and CBC testing.
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Case Study 2: Hemoconcentration
Background: Patient with suspected Ebola Virus symptoms admitted for evaluation. Isolation protocols were in effect. A handheld blood gas chemistry analyzer served as the primary chemistry analyzer. 0853 hrs – Specimens collected for chemistry and CBC testing.
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Case Study 2: Hemoconcentration
Background: Patient with suspected Ebola Virus symptoms admitted for evaluation. Isolation protocols were in effect. A handheld blood gas chemistry analyzer served as the primary chemistry analyzer. 0853 hrs – Specimens collected for chemistry and CBC testing.
Handheld Results Hct = 68% Hb = 21.9 g/dL
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Case Study 2: Hemoconcentration
Background: Patient with suspected Ebola Virus symptoms admitted for evaluation. Isolation protocols were in effect. A handheld blood gas chemistry analyzer served as the primary chemistry analyzer. 0853 hrs – Specimens collected for chemistry and CBC testing.
Handheld Results Hct = 68% Hb = 21.9 g/dL
CBC Results Hct = 41% Hb = 13.2 g/dL
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Case Study 2: Hemoconcentration
Background: Patient with suspected Ebola Virus symptoms admitted for evaluation. Isolation protocols were in effect. A handheld blood gas chemistry analyzer served as the primary chemistry analyzer. 0853 hrs – Specimens collected for chemistry and CBC testing.
Hct = 43% Hb = 13.8 g/dL
Handheld Results Hct = 68% Hb = 21.9 g/dL RE-MIXING!
CBC Results Hct = 41% Hb = 13.2 g/dL
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Case Study 2: Hemoconcentration
Background: Patient with suspected Ebola Virus symptoms admitted for evaluation. Isolation protocols were in effect. A handheld blood gas chemistry analyzer served as the primary chemistry analyzer. 0853 hrs – Specimens collected for chemistry and CBC testing.
Hct = 43% Hb = 13.8 g/dL
Inadequate mixing may result in artificial changes in total hemoglobin measurements.
Handheld Results Hct = 68% Hb = 21.9 g/dL RE-MIXING!
CBC Results Hct = 41% Hb = 13.2 g/dL
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Electrode
Conductance (Impendence)
Contemporary Hemoglobinometric Techniques
• Plasma protein content contributes to hematocrit measurements for conductance-based systems.
= Plasma Protein
High Resistance
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Electrode
Conductance (Impendence)
Contemporary Hemoglobinometric Techniques
= Plasma Protein
• Plasma protein content contributes to hematocrit measurements for conductance-based systems.
• Conductance-based systems assumes a relatively fixed protein concentration. Therefore, during hemodilution, hematocrit may be falsely lower and causing an underestimation of total hemoglobin.
Low Resistance from low plasma protein concentration!
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Electrode
Conductance (Impendence)
Contemporary Hemoglobinometric Techniques
= Plasma Protein
• Plasma protein content contributes to hematocrit measurements for conductance-based systems.
• Conductance-based systems assumes a relatively fixed protein concentration. Therefore, during hemodilution, hematocrit may be falsely lower and causing an underestimation of total hemoglobin.
• UCDMC Study: Comparison of a handheld blood gas analyzer using conductance-based measurement of hemoglobin versus a benchtop blood gas analyzer using a spectrophotometric-based method for hemoglobinometry.
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• Sixty patients requiring cardiac surgery were evaluated.
• Paired specimens were tested using a handheld POC analyzer and spectrophotometric methods through the core laboratory.
• Mean (SD) bias was -1.4 (1.1) g/dL, P = 0.011.
• Based on core laboratory results 12 patients would have received unnecessary transfusions.
Clinical Impact of Hemodilution for Point-of-Care Hemoglobin Measurements
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• Sixty patients requiring cardiac surgery were evaluated.
• Paired specimens were tested using a handheld POC analyzer and spectrophotometric methods through the core laboratory.
• Mean (SD) bias was -1.4 (1.1) g/dL, P = 0.011.
• Based on core laboratory results 12 patients would have received unnecessary transfusions.
Clinical Impact of Hemodilution for Point-of-Care Hemoglobin Measurements
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• Sixty patients requiring cardiac surgery were evaluated.
• Paired specimens were tested using a handheld POC analyzer and spectrophotometric methods through the core laboratory.
• Mean (SD) bias was -1.4 (1.1) g/dL, P = 0.011.
• Based on core laboratory results 12 patients would have received unnecessary transfusions.
Clinical Impact of Hemodilution for Point-of-Care Hemoglobin Measurements
= $219
$219 x 12 = $2,628 POTENTIALLY WASTED
Toner RW, et al. Appl Health Econ Health Policy 2011;9:29-37
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Case Study 3: Hemodilution
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Case Study 3: Hemodilution
Background: FDA MAUDE database reports a case (03P76-25) of a neonatal patient with discrepant point-of-care (POC) hemoglobin values compared to the laboratory. The POC device used a conductance-based method of hemoglobin measurement, while the laboratory used a spectrophotometric method.
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Case Study 3: Hemodilution
Background: FDA MAUDE database reports a case (03P76-25) of a neonatal patient with discrepant point-of-care (POC) hemoglobin values compared to the laboratory. The POC device used a conductance-based method of hemoglobin measurement, while the laboratory used a spectrophotometric method. • POC device reported a hematocrit of 22%. Physician administered 7 mL of
blood based on the POC result.
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Case Study 3: Hemodilution
Background: FDA MAUDE database reports a case (03P76-25) of a neonatal patient with discrepant point-of-care (POC) hemoglobin values compared to the laboratory. The POC device used a conductance-based method of hemoglobin measurement, while the laboratory used a spectrophotometric method. • POC device reported a hematocrit of 22%. Physician administered 7 mL of
blood based on the POC result.
• Transfusion was stopped halfway after the laboratory reported a hematocrit of 40% and hemoglobin of 11.7 g/dL.
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Case Study 3: Hemodilution
Background: FDA MAUDE database reports a case (03P76-25) of a neonatal patient with discrepant point-of-care (POC) hemoglobin values compared to the laboratory. The POC device used a conductance-based method of hemoglobin measurement, while the laboratory used a spectrophotometric method. • POC device reported a hematocrit of 22%. Physician administered 7 mL of
blood based on the POC result.
• Transfusion was stopped halfway after the laboratory reported a hematocrit of 40% and hemoglobin of 11.7 g/dL.
• Post-transfusion POC and lab hematocrit values were 45 and 50% respectively.
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Analytical Performance of Optical vs. Conductance-Based Hemoglobinometry
Dev
ice
#1 H
b (g
/dL)
Central Laboratory Hb (g/dL)
y = 0.5092x + 4.0176 R² = 0.5253
4
5
6
7
8
9
10
11
4 5 6 7 8 9 10 11 12
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Analytical Performance of Optical vs. Conductance-Based Hemoglobinometry
Dev
ice
#2 H
b (g
/dL)
Central Laboratory Hb (g/dL)
y = 0.5249x + 3.9443 R² = 0.5407
4
5
6
7
8
9
10
11
4 5 6 7 8 9 10 11 12
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Analytical Performance of Optical vs. Conductance-Based Hemoglobinometry
Dev
ice
#3 H
b (g
/dL)
y = 0.9345x + 0.4057 R² = 0.9205
4
5
6
7
8
9
10
11
4 5 6 7 8 9 10 11
Central Laboratory Hb (g/dL)
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Analytical Performance of Optical vs. Conductance-Based Hemoglobinometry
Notes: Reference Method = Beckman LH hematology analyzer
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Analytical Performance of Optical vs. Conductance-Based Hemoglobinometry
Notes: Reference Method = Beckman LH hematology analyzer
Median (IQR) Bias: 0.78 (0.78) g/dL P < 0.001 N = 50
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Analytical Performance of Optical vs. Conductance-Based Hemoglobinometry
Notes: Reference Method = Beckman LH hematology analyzer
Median (IQR) Bias: 0.73 (0.60) g/dL P < 0.001 N = 50
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Analytical Performance of Optical vs. Conductance-Based Hemoglobinometry
Notes: Reference Method = Beckman LH hematology analyzer
Median (IQR) Bias: 0.22 (0.20) g/dL P = 0.510 N = 50
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Analytical Performance of Optical vs. Conductance-Based Hemoglobinometry
Notes: *** P<0.001, Central Lab = Spectrophotometric Method, n = 20 patients
6
6.5
7
7.5
8
8.5
9
9.5
10
1 2 3 4 5
Tota
l Hem
oglo
bin
(g/d
L)
Time Point
Serial Testing Performance at 7 and 8 g/dL • Serial testing revealed significant analytical
bias between spectrophotometry vs. conductance-based measurements.
*** Spectrophotometric-based Methods
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Analytical Performance of Optical vs. Conductance-Based Hemoglobinometry
Notes: *** P<0.001, Central Lab = Spectrophotometric Method, n = 20 patients
6
6.5
7
7.5
8
8.5
9
9.5
10
1 2 3 4 5
Tota
l Hem
oglo
bin
(g/d
L)
Time Point
Serial Testing Performance at 7 and 8 g/dL • Serial testing revealed significant analytical
bias between spectrophotometry vs. conductance-based measurements.
*** Spectrophotometric-based Methods
Conductance-based Methods
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Analytical Performance of Optical vs. Conductance-Based Hemoglobinometry
6
6.5
7
7.5
8
8.5
9
9.5
10
1 2 3 4 5
Tota
l Hem
oglo
bin
(g/d
L)
Time Point
Serial Testing Performance at 7 and 8 g/dL • Serial testing revealed significant analytical
bias between spectrophotometry vs. conductance-based measurements.
• Conductance-based devices would have prompted unnecessary transfusions at time point #5 for patients using the 7 g/dL cutoff.
Unnecessary Transfusion Risk
***
Notes: *** P<0.001, Central Lab = Spectrophotometric Method, n = 20 patients
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Analytical Performance of Optical vs. Conductance-Based Hemoglobinometry
6
6.5
7
7.5
8
8.5
9
9.5
10
1 2 3 4 5
Tota
l Hem
oglo
bin
(g/d
L)
Time Point
Serial Testing Performance at 7 and 8 g/dL • Serial testing revealed significant analytical
bias between spectrophotometry vs. conductance-based measurements.
• Conductance-based devices would have prompted unnecessary transfusions at time point #5 for patients using the 7 g/dL cutoff.
• All serial conductance measurements were at risk for potential transfusions if the 8 g/dL cutoff was used.
Unnecessary Transfusion Risk
***
Notes: *** P<0.001, Central Lab = Spectrophotometric Method, n = 20 patients
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Analytical Performance of Optical vs. Conductance-Based Hemoglobinometry
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Central Laboratory Method
Tota
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Time Point
Serial Testing Performance at 7 and 8 g/dL • Serial testing revealed significant analytical
bias between spectrophotometry vs. conductance-based measurements.
• Conductance-based devices would have prompted unnecessary transfusions at time point #5 for patients using the 7 g/dL cutoff.
• All serial conductance measurements were at risk for potential transfusions if the 8 g/dL cutoff was used.
Unnecessary Transfusion Risk
***
Notes: *** P<0.001, Central Lab = Spectrophotometric Method, n = 20 patients
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Manufacturer and User Facility Device Experience (MAUDE) Database Summary
Device 1 Device 2 Device 3 Timeframe 2011-2016 2011-2016 2014-2016* Erroneous Results 8 0 0 Improper Transfusions
5 0 0
https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfmaude/results.cfm, Accessed on July 19, 2016
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INTERFERENCES IN WHOLE BLOOD ANALYSIS
Air Contamination
Delayed Testing
Hemolysis
Hemodilution/Hemoconcentration
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INTERFERENCES IN WHOLE BLOOD ANALYSIS
Air Contamination
Delayed Testing
Hemolysis
Hemodilution/Hemoconcentration Pseudohyperkalemia
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INTERFERENCES IN WHOLE BLOOD ANALYSIS
Air Contamination
Delayed Testing
Hemolysis
Hemodilution/Hemoconcentration Pseudohyperkalemia “Pseudonormokalemia”
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INTERFERENCES IN WHOLE BLOOD ANALYSIS
Air Contamination
Delayed Testing
Hemolysis
Hemodilution/Hemoconcentration Pseudohyperkalemia “Pseudonormokalemia”
No current FDA approved integrated solutions for detecting hemolysis at the point-of-care
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Biotin: The “Snake Oil” of 2018?
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Biotin and Cardiac Troponin Testing
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Mumma B, et al. AACC Poster Presentation 2018
• 1,443 Gen 5 troponin T samples tested (0-hour, n = 797; 3-hour, n=646) from 850 patients.
Estimating the Probability of Biotin Interference
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Mumma B, et al. AACC Poster Presentation 2018
• 1,443 Gen 5 troponin T samples tested (0-hour, n = 797; 3-hour, n=646) from 850 patients.
• Biotin not detectable in 471 (59%) and 399 (62%) 3-hour samples.
Estimating the Probability of Biotin Interference
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• 1,443 Gen 5 troponin T samples tested (0-hour, n = 797; 3-hour, n=646) from 850 patients.
• Biotin not detectable in 471 (59%) and 399 (62%) 3-hour samples.
• Only one 0-hour sample and one 3-hour sample had biotin >20 ng/mL (0.13% [95% CI: 0-0.7%]).
Mumma B, et al. AACC Poster Presentation 2018
Estimating the Probability of Biotin Interference
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Mumma B, et al. AACC Poster Presentation 2018
Estimating the Probability of Biotin Interference
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Estimating the Probability of Biotin Interference
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Adult ED Patients with Unknown Biotin Status: 540 Average Plasma Biotin: 1.15 (0.97) ng/mL
Specimens collected as part of clinical validation
UC Davis Cardiac Troponin Patients
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Adult ED Patients with Unknown Biotin Status: 540 Average Plasma Biotin: 1.15 (0.97) ng/mL
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20
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Num
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Biotin Concentration (ng/mL)
Gen 5 TnT Biotin Interference Threshold is 20 ng/mL
Biotin quantified by GC-TOF-MS
UC Davis Cardiac Troponin Patients
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Adult ED Patients with Unknown Biotin Status: 540 Average Plasma Biotin: 1.15 (0.97) ng/mL
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120
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Num
ber o
f Pat
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Biotin Concentration (ng/mL)
Gen 5 TnT Biotin Interference Threshold is 20 ng/mL
Biotin quantified by GC-TOF-MS
BIOTIN IS LESS LIKELY TO BE A PROBLEM IN CARDIAC TROPONIN TESTING AND IS POPULATION SPECIFIC!
UC Davis Cardiac Troponin Patients
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Biotin and Urine Pregnancy Testing
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Biotin Interference with Urine Pregnancy Tests
• Recent studies show some point-of-care urine pregnancy tests were affected by biotin.
• Biotin is cleared by the kidneys.
• In this study, the QuickVue urine pregnancy test exhibited interference as low as 6 microgram/mL of urine biotin!
Williams G, et al. Clin Biochem 2018;53:168-170
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Best POCT Practices for Mitigating Interfering Substances
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• Education: The laboratory must be the leader in educating providers and patients of potential test interferences. Go to grand rounds, build partnerships, and provide multi-modality means to disseminate knowledge.
POCT Best Practices for Interferences
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• Education: The laboratory must be the leader in educating providers and patients of potential test interferences. Go to grand rounds, build partnerships, and provide multi-modality means to disseminate knowledge.
POCT Best Practices for Interferences
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• Education: The laboratory must be the leader in educating providers and patients of potential test interferences. Go to grand rounds, build partnerships, and provide multi-modality means to disseminate knowledge.
• Surveillance: Know your population! Collect data and determine if your local population may be be at risk for certain interferences (e.g., biotin, vitamin C, etc). MAUDE database is also helpful!
POCT Best Practices for Interferences
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• Education: The laboratory must be the leader in educating providers of potential test interferences. Go to grand rounds, build partnerships, and provide multi-modality means to disseminate knowledge.
• Surveillance: Know your population! Collect data and determine if your local population may be be at risk for certain interferences (e.g., biotin, vitamin C, etc). MAUDE database is also helpful!
• Electronic Early-Warning Systems: Leverage electronic solutions. Ordering of susceptible tests could flag both on the provider and laboratory side certain substances are identified.
POCT Best Practices for Interferences
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Conclusions • Interfering substances are out there and
impact POC testing as much as traditional lab testing!
• Interferences in common POC devices such as glucose meters have resulted in injury and death.
• Interferences in whole blood analysis have resulted in inappropriate treatment decisions.
• Medications and supplements may also affect POC immunoassays such as urine pregnancy tests.
• Education and awareness is critical to minimizing errors associated with interfering substances.
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Questions?