collection of specimens

8/12/2019 Collection of Specimens

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Criteria for rejection of specimens

Criteria should be developed by a laboratory on the basis of which the processing of aspecimen may not be done by the laboratory. The following are some examples:

Missing or inadequate identification.

Insufficient quantity.

pecimen collected in an inappropriate container.

Contamination suspected.

Inappropriate transport or storage.

!n"nown time delay.

#aemolysed blood sample.

Collection of specimens

The clinical state of the patient will not necessarily be reflected by the result of laboratoryinvestigation despite correct laboratory performanceunless the specimen is in optimal

condition required for the analysis. ome of the important specimens and their propercollection and transportation methods are described here so as to ensure quality.

$lood

%hole blood is required for bacteriological examination. erum separated from blood isused for serological techniques. "in antisepsis is extremely important at the time ofcollection of the sample. Tincture of iodine &'()*+, povidone iodine &'-*+ andchlorhexidine &-. * in /-* alcohol+ are ideal agents. #owever, some individuals may behypersensitive to iodine present in some of these. %hile collecting blood for culture,thefollowing points must be remembered:

Collect blood during the early stages of disease since the number of bacteria in bloodis higher in the acute and early stages of disease.

Collect blood during paroxysm of fever since the number of bacteria is higher at hightemperatures in patients with fever.



In the absence of antibiotic administration, 00* culture positivity can be seen withthree blood cultures.

mall children usually have higher number of bacteria in their blood as compared toadults and hence less quantity of blood needs to be collected from them &Table )+.

Table ): 1olume of blood to be collected at different ages

2ge 1olume in ) bottles

3 ) years ) ml

)( years 4 ml

5('- years ') ml

6'- years )- ml

Cerebrospinal fluid &C 7+

8xamination of C 7 is an essential step in the diagnosis of any patient with evidence ofmeningeal irritation or affected cerebrum. 2lmost 9('- ml of C 7 is collected and part ofit is used for biochemical, immunological and microscopic examination and remainingfor bacteriological or fungal examination. The following important precautions need to beta"en for C 7 collection and transportation:

Collect C 7 before antimicrobial therapy is started.

Collect C 7 in a screw capped sterile container and not in an injection vial withcotton plug.

;o not delay transport and laboratory investigations.

Transport in a transport medium if delay in processing is unavoidable.

C 7 is a precious specimen, handle it carefully and economically. It may not be possible to get a repeat specimen.



<erform physical inspection immediately after collection and indicate findings onlaboratory requisition form.

tore at 9/oC, if delay in processing is inevitable.

The characteristics of the appearance of C 7 are outlined in Table 9.

Table 9: 2ppearance and interpretations of C 7

Clear and colourless =ormal

Clear with Tyndall effect&spar"ling appearance against incident light+

#igh protein content

Clear yellowish >ld haemolysis

Clear red 7resh haemolysis

Turbid blood(stained #aemorrhage

Turbid white #igh cell or protein content

Turbid clot &after overnight storage+ 7ibrin clots

putum

putum is processed in the laboratory for aetiological investigation of bacterial andfungal infections of the lower respiratory tract. It is of utmost importance in the diagnosisof pulmonary tuberculosis.

elect a good wide(mouthed sputum container, which is preferably disposable, madeof clear thin plastic, unbrea"able and lea" proof material.

?ive the patient a sputum container with the laboratory serial number written on it.how the patient how to open and close the container and explain the importance of not

rubbing off the number written on the side of the container.

Instruct the patient to inhale deeply )(9 times, cough up deeply from the chest andspit in the sputum container by bringing it closer to the mouth.

Ma"e sure the sputum sample is of good quality. 2 good sputum sample is thic", purulent and sufficient in amount &)(9 ml+.



?ive the patient an additional container with laboratory serial number written on it for anearly morning specimen. 8xplain to the patient to rinse his@her mouth with plain water

before bringing up the sputum.

!rine

!nder normal circumstances urine is sterile. The lower part of the urethra and thegenitalia are normally colonised by bacteria, many of which may also cause urinary tractinfection. ince urine is a good growth medium for all sorts of bacteria, proper andaseptic collection assumes greater importance for this specimen.

7or microbiological examination urine must be collected as a Aclean catch(mid(streamAspecimen.

!rine specimens should be transported to the laboratory within one hour for bacteriological examination, because of the continuous growth of bacteria in vitro thus

altering the actual concentration of organisms.

tool

7aecal specimens for the aetiological diagnosis of acute infectious diarrheaBs should becollected in the early stage of illness and prior to treatment with antimicrobials. 2 stoolspecimen rather than a rectal swab is preferred.

The 7aeces specimen should not be contaminated with urine.

;o not collect the specimen from bed pan.

Collect the specimen during the early phase of the disease and as far as possible before the administration of antimicrobial agents.

' to ) gm quantity is sufficient.

If possible, submit more than one specimen on different days.

The fresh stool specimen must be received within '() hours of passage.

tore at )(4oC.

Modified Cary and $lair medium is recommended as a good transport medium. It is avery stable medium and can be stored for use in screw capped containers. It is a semi(solid transport medium. 2t least two swabs should be inoculated. Most pathogens willsurvive for up to 4 hours at room temperature. pecimens are unacceptable if themedium is held for more than one wee" or if there is detectable drying of the specimen.



2lternative transport media are 1en"ataraman(Dama"rishnan medium &1(D fluid+ oral"aline peptone water. 1D fluid should be prepared in 9- ml &' oE+ screw capped bottles&MacCartney bottles+. It preserves vibrios for more than six wee"s and has also proved to

be a very convenient medium for transportation as it can be "ept at room temperatureafter collection of the specimen.

Transportation of specimens

pecimens to be sent to other laboratories require special attention for safe pac"ing of thematerial. ?uidelines are usually issued by national authorities and the same should bestrictly followed. 7or hand(carried transportation over a short distance, the specimenshould be placed upright in appropriate rac"s. 7or long distance transportation, it should

be placed in three containers, i.e:

2 primary container which has the specimen and is lea" proof with a screw(cap.

2 secondary container which is durable, waterproof and made of metal or plastic witha screw(cap. It should have enough absorptive material to absorb the contents of the primary container should the latter brea" or lea". >n its outside, the details of thespecimen should be pasted.

2 tertiary container is usually made of wood or card box. It should be capable ofwithstanding the shoc"s and trauma of transportation. ;ry ice can be "ept between thisand the secondary container along with sufficient absorbents and provision for the escapeof carbon dioxide to prevent a pressure build(up inside.

In general, most specimens should be processed in the laboratory within ' to ) hours after

collection. In practice, a )(to (hour time limit is probably more practical during a normalwor"ing day. The laboratory must be organiEed to permit processing of the specimens assoon as they arrive, and the collection of most specimens should be limited to thewor"ing hours of the laboratory. #owever, some arrangements must be made to allow forthe initial handling of the few specimens that have to be collected outside of thelaboratoryBs wor"ing hours.

collection of specimens

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