LABORATORY TESTING IN

PRIMARY CARE OPTOMETRY

Tammy P. Than, MS, OD, FAAOCarl Vinson VAMC

Dublin, GA

tammy.than@va.gov

Microbiology

Cultures and Sensitivities

• Mandatory central corneal ulcers hyperacute conjunctivitis ophthalmia neonatorum membranous conjunctivitis Parinaud’s oculoglandular syndrome postoperative infections

• Recommended chronic conjunctivitis unresponsive conjunctivitis new practitioner

Cultures and Sensitivities

• specimen preparation is important• no anesthetic – if possible• sterile swab plate onto culture media• culturette• media:

Thioglycolate broth Blood agar Chocolate agar Saboraud’s agar

Transport Media

• Amies media without charcoal Higher yield than other media Comparable to plates

In-Office Microbiology

• Gram Stain Gram (+) = purple Gram (-) = pink look at morphology

• Cytology PMNs = bacterial lymphocytes = viral eosinophils = allergic

Diagnostic Imaging

• plain film X-Ray• CT scan• MRI

75 million in 2003

• Ultrasonography• Angiography• GDx, OCT, HRT• etc…

Resources

• Imaging of the Globe and Orbit: A Guide to Differential Diagnosis Hosten and Bornfield Publisher Thieme

• http://www.med.harvard.edu/AANLIB/home.html

• http://www.loni.ucla.edu/index.shtml

X-Ray: The Basics

• Incident X-Ray enters tissue• Beam is attenuated• Exit X-Ray leaves tissue exposes film

White areas = not exposed Dark areas = film exposed

• 3-D represented by 2-D• Black = air (no attenuation)• White = bone• Gray = soft tissue

X-Ray: Types of Views

• Skull / Sinus Series Caldwell Lateral Waters

• Chest AP, PA, lateral

• Spinal

CALDWELL

CALDWELCALDWELLL

LATERAL

LATERALLATERAL

WATERS

WATERSWATERS

X-Ray Indications• Confirm the integrity of the orbit

Intraocular Foreign Body Intraorbital Foreign Body

• Trauma muscle entrapment?

X-Ray Indications

• Sinusitis R/O Orbital cellulitis

• Horner’s syndrome

• Uveitis

• Ankylosing spondylitis

• Reiter’s syndrome

X-Ray: Contraindications

• Pregnancy• Excessive Radiation Exposure

Rad = unit of absorbed energy in tissue Gray (Gy) = 100 Rad

the “latest” unit 1 Gy = 100 cGy chest X-Ray is < 1 cGy cancer treatment may be 6000 cGy lens is most sensitive

X-Rays

• Pros Inexpensive Readily available Rapid results

• Cons Radiation exposure No information about soft tissue 2-D interpretation can be difficult

Case #1

• 17 YOM

• Hit in eye x 1 day

• + pain

• +diplopia

Work-Up

• EOMs

• Exophthalmometry

• Crepitus?

• Nerve sensation

• IOP

• Imaging

Management

• Nasal decongestants

• Oral antibiotics broad spectrum

e.g. Keflex 500 mg qid

• Don’t blow nose!

• +/- Sx in 1-2 weeks

Other Considerations…

• R/O Seidel’s sign

• Anterior Segment Pathology uveitis corneal abrasion subconjunctival hemorrhage

• Commotio Retinae

CT Scan: The Basics• Series of thin X-Ray sections

flat panel detectors may eliminate slices

• Emitted X-Rays

• Diode sensors

• Computer reconstructs views

CT Scan: The Basics

• CT Numbers density < water = negative CT# density > water = positive CT#

• “Windowing”

• Gray Scale White = bone Black = air Gray = brain

CT Scan• Views

coronal paranasal sinuses, orbital integrity

sagittal chiasmal pathology

axial orbital and visual pathways

CT – The Exam• Specific protocols

orbital chiasmal brain sinuses

• Slice thickness and slice increment• Cranial

~1 cm / no overlap

• Orbital and Chiasmal 3 mm with 2 mm between allows overlap

• Gantry• 10-20 minutes / scan

Contrast

• Iodine good agent for photoelectric capture enhances visibility of vascular lesions

• Administered IV (or intrathecal)• 1:40,000 incident of AE• BUN and Creatinine• NPO• Good medication hx

d/c Metformin (Glucophage) prior to procedure

• CI is shellfish allergy

BUN (Blood Urea Nitrogen)

• actually performed on serum or plasma 12% higher than blood

• nitrogen portion of urea• urea is formed in liver from protein breakdown• filtered through renal glomeruli

small amount reabsorbed in the tubules remainder excreted in urine

• azotemia – elevated BUN nonspecific prerenal, renal, or postrenal

BUN (Blood Urea Nitrogen)

• must be compared over time or evaluated with other tests renal function – also assess creatinine levels

• fasting not required• Adult 5-20 mg/dL• >60 8-21 mg/dL• increased BUN

many conditions and many drugs

• decreased BUN alcohol abuse, diet lacking protein, liver destruction, late

pregnancy

CREATININE

• product of anaerobic energy-producing creatine-phosphate metabolism in skeletal muscle

• excreted by kidneys increased levels indicative of decreased glomerular

filtration rate

• Avoid excessive exercise for 8 hours and avoid excessive red meat for 24 hours before testing

CREATININE

• Normal females 0.5 – 1.1 mg/dL males 0.6 –1.2 mg/dL elderly – may be lower

• Creatinine clearance, urine 24 hour collection

• Creatinine clearance, serum urine 6, 12, or 24 hour collection blood sample collected anytime during urine collection

period

CT Scan: Artifacts

• Motion

• Dental Fillings

• Partial volume phenomenon

CT Indications

• bone imaging

• calcification

• blood detection acute

• meningiomas

• when MRI contraindicated

CT Contraindications

• pregnancy

• excessive radiation exposure

• contrast contraindication iodine sensitivity shellfish allergy kidney disease

CT Scan

• Pros High diagnostic yield Good for bone Can reconstruct different views

• Cons Expensive Human risk Motion artifacts Hard to ddx tumors

MRIUnpaired protons (H) = tiny magnets

from water and fat body is 63% hydrogen atoms

• Disrupt with radio pulse

• Protons return to original state

• Release energy -> MRI

MRI

• Signal strength: proton density• Relaxation time: surrounding tissue• T1 weighted

Proton density tissue composition

• T2 weighted Tissue differences

• Intermediate• fat suppression

MRI

• White Matter and Fat T1 = bright T2 = dark

• Gray Matter and CSF T1 = dark T2 = bright

• Vitreous T1 = dark T2 = bright

• blood, air = black• EOMs and optic nerves = intermediate density

MRI: The Examination

• Gantry• Flux

0.5 – 1.5 Tesla

• Energy detected• Image reconstructed• 40 minutes• +/- gadolinium contrast

paramagnetic highlights images of similar density

MRI Indications

• tumors posterior visual pathway brain stem pituitary

• infarcts• posterior fossa• MS

MRI Indications• elevated optic nerve head(s)

• unilateral proptosis

• field loss hemianopia bitemporal

• cranial nerve palsies

MRI Contraindications

• pregnancy

• metallic FB

• pacemakers

• kidney disease (if using contrast)

• claustrophobia?

Latest…• Short bore

high field >1.5 Tesla advantages of tunnel and open MRIs

MRI

• Pros More accurate 3-D image Good structural detail No radiation

• Cons $$$ Time consuming Won’t show recent hemorrhage

Case #3.

• 46 YOWF

• CC: Time to change her glasses

• HabRx: OD –4.25 DS OS –5.00 DS

• BVA OD: -4.00 20/20 OS: -0.25 20/20

Other Imaging Tests…

Magnetic Resonance Angiography (MRA)

• Non-invasive method for investigation of blood vessels

• Surgical planning

• 3-D view

• Picks up rapid blood flow

• highly accurate for stenosis >50%

Positron Emission Tomography (PET)

• Biochemical and physiologic function – in vivo

• Radioactive “Tracer” compound Injected or inhaled C, N, O, F

18F labeled fluorodeoxyglucose Image of brain activity

Functional MRI (fMRI)

• Physiology of visual system

• With or without contrast

• Many advantages over PET

• The new “lie detector?”

So… You want to order a scan??

Before You Order Tests...

• Good case history any contraindications??

• Comprehensive exam• Narrow ddx• Is there anything YOU can do?• Avoid “fishing expedition” or “shot-gun”

approaches• Select most appropriate test

MRI not always needed

Communicating with the Lab

• Which test(s)? with contrast?

• Code?• Which insurance?• What do you want to view?• DDX?• Be available

Getting the Job Done

• Communicate with the Patient Explain why imaging is necessary Explain the test

• Insurance Issues Can you order the test?? Is the patient insured??

If You Order Tests...

• Written report of findings and copies of the films

• Communicate

• Treat

• Comanage / Refer

CLIA

• Clinical Laboratory Improvement Act

• regulates all lab tests performed on humans in US

• ensures quality laboratory testing

• Waived tests determined by FDA or CDC to be so simple that

there is little risk of error

• www.cms.hhs.gov/clia

Missouri Contact

• Missouri Dept of Health and Senior Services – CLIA Section PO Box 570 Jefferson City, MO 65102 573-751-6318 Contact: William Nugent

CLIA

• can file for “Waived Status” approximately 40 tests

random blood glucose ESR urine pregnancy tests

• must meet criteria: enroll in CLIA program pay fees biennially ($150 for waived) follow manufacturers’ test instructions

Glad you looked!

• 58 year old female

• CC: SpRx broken

• OHx: unremarkable

• MHx: unremarkable, no meds

• 20/20 OD; 20/20 OS

Random Blood Glucose

• note when patient ate last e.g. 220 mg/dL pp 3 hours pp = post-prandial

• diabetic if: 200 mg/dL with symptoms

• can do in-office

• encourage patients to do this!

Fasting Plasma Glucose

• no food or drink for 8-12 hours

• diabetes if 126 mg/dL must repeat if asymptomatic

• IFG = 100 – 125 mg/dL

• also increased with: steroids stress diuretics

What’s in a Name??

• home monitoring whole blood glucose

• laboratory methods plasma glucose

• plasma glucose usually 10-15% higher than whole blood

• SOME home monitors calibrate to plasma

Oral Glucose Tolerance Test (OGTT)

• 75 g oral glucose

• check urine and blood at intervals

• non-diabetic BS will return to fasting levels in 3 hours

• diabetic if 200 mg/dL at 2 hours

• impaired GT if 140 and < 200 mg/dL at 2 hours

• not needed if FBS > 200 mg/dL

Glycosylated Hemoglobin

• HbA1c

• checks long-term control• glycosylated HgB stays with RBC for its entire life• not diagnostic test?• normal = 4.3-6.1%

• diabetic goal < 7.0%• ask patients!• A1cNow (Metrika, Inc.) • A1C Now InView multitest system

CPT 83036QW

Glycoslyated HemoglobinA1C Blood Glucose

Levels

12% 345 mg/dL

11 310

10 275

9 240

8 205

7 170

6 135

5 100

4 65

1% A1C = 30 mg/dL1% A1C = 30 mg/dL

What Can We Do?• Pre-diabetes – new term!• 61% of US adults overweight• Diabetes Prevention Program

pts with IGT (N=3234) lifestyle changes vs metformin vs placebo reduced risk

58% with lifestyle– 30 minutes daily activity; weight loss of 5-7% BW30 minutes daily activity; weight loss of 5-7% BW

31% with medication

• Educate patients honesty best policy…

Make Sure Your Diabetics Know Their ABCs• A1c

< 7.0%

• Blood Pressure < 130/80

• Cholesterol LDL <100 mg/dL HDL > 45 Triglycerides < 200 statin use if TC 135 mg/dL

• www.diabetes.org 67% didn’t know! Diabetes PHD (personal health decisions)

Fasting Plasma Glucose

• fluctuating vision get stable reading before new SpRx

• retinopathy

• diplopia

• vascular occlusions

• optic neuropathy

HIV Testing

• Home-use HIV test kits NOT FDA approved Available on Internet

• FDA-approved Home sample collection kits

• Enzyme Immunoassay

• Western Blot

• Nucleic acid testing (viral load)

OraQuick Rapid HIV-1/2 Antibody Test

• approved in 2002 for testing with blood HIV-1 and HIV-2 CLIA waived status

• March 26, 2004 approved using oral fluid results in 20 minutes! only for HIV-1 not for screening blood donors not CLIA waived status yet

• 31% do NOT return for HIV testing results• Also Uni-Gold Recombigen HIV (7/2004)