COLLECTION OF CLINICAL SPECIMENS

COLLECTION OF CLINICAL SPECIMENS

(i) BLOOD

• Whole blood is required for bacteriological examination.
• Serum separated from blood is used for Serological techniques.
• Skin antisepsis is extremely important at the time of collection of the sample.
• Tincture of iodine (1 – 2 %), Povidone iodine (10 %) and Chlorhexidine (0.5 % in 70 % Alcohol) are ideal agents. However, some individuals may be hypersensitive to iodine present in some of these.
• Collect blood during the early stages of disease since the number of bacteria in blood is higher in the acute and early stages of disease.
• Collect blood during Paroxysm (a sudden recurrence of symptoms) of fever since the number of bacteria is higher at high temperatures in patients with fever.
• In the absence of antibiotic administration, 99 % culture positivity can be seen with three blood cultures.
• Small children usually have higher number of bacteria in their blood as compared to adults and hence less quantity of blood needs to be collected from them.

(ii) CEREBROSPINAL FLUID (CSF)

• Examination of CSF is an essential step in the diagnosis of any patient with evidence of meningeal irritation or affected cerebrum.
• Almost 3 - 10 ml of CSF is collected and part of it is used for biochemical, immunological and microscopic examination and remaining for bacteriological or fungal examination.
• Collect CSF before antimicrobial therapy is started.
• Collect CSF in a screw – capped sterile container and not in an injection vial with cotton plug.
• Do not delay transport and laboratory investigations.
• Transport in a transport medium if delay in processing is unavoidable.
• CSF is a precious specimen, handle it carefully and economically. It may not be possible to get a repeat specimen.
• Perform physical inspection immediately after collection and indicate findings on laboratory requisition form.
• Store at 37 °C, if delay in processing is inevitable. 

Appearance and Interpretation of CSF

S.No	Appearance	Interpretation of CSF
1	Clear and colourless	Normal
2	Clear and Tyndall effect (sparkling appearance against incident light)	High protein content
3	Clear Yellowish	Old Haemolysis
4	Turbid – Blood stained	Fresh Haemolysis
5	Clear red	Haemorrhage
6	Turbid white	High cell or Protein content
7	Turbid clot (after overnight storage)	Fibrin clots

 

(iii) SPUTUM

• Sputum is processed in the laboratory for etiological investigation (cause of disease) of bacterial and fungal infections of the Lower respiratory tract.
• It is of utmost importance in the diagnosis of Pulmonary tuberculosis.
• Give the patient an additional container with laboratory serial number written on it for an early morning specimen.
• Explain to the patient to rinse his/her mouth with plain water before bringing up the sputum.
• Select a good wide-mouthed sputum container, which is preferably disposable, made of clear thin plastic, unbreakable and leak proof material.
• Give the patient a sputum container with the laboratory serial number written on it.
• Show 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 2 - 3 times, cough up deeply from the chest and spit in the sputum container by bringing it closer to the mouth.
• Make sure the sputum sample is of good quality. A good sputum sample is thick, purulent and sufficient in amount (2 - 3 ml).

(iv) URINE

• Under normal circumstances urine is sterile. The lower part of the urethra and the genitalia are normally colonized by bacteria, many of which may also cause urinary tract infection. Since urine is a good growth medium for all sorts of bacteria, proper and aseptic collection assumes greater importance for this specimen.
• For microbiological examination urine must be collected as a "clean catch-mid-stream" specimen.
• Urine 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.

(v) STOOL

• Faecal specimens for the aetiological diagnosis of acute infectious diarrhoeas should be collected in the early stage of illness and prior to treatment with antimicrobials.
• The faeces specimen should not be contaminated with urine.
• Do 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. One to two gram quantity is sufficient.
• Modified Cary and Blair medium is recommended as a good transport medium. It is a very stable medium and can be stored for use in screw – capped containers. It is a semi-solid transport medium.

(vi) THROAT SWAB

• Depress the tongue with a Tongue blade.
• Swab the inflammed area of the throat, pharynx or tonsils with a sterile swab taking care to collect the pus or piece of membrane.
• Transport in sterile transport tube.

(vii) HAIR

• Pluck out hair by the roots with sterile forceps.
• Choose hairs that are broken and scaly.
• Place the specimen in a sterile petridish for processing. Transport to the lab.

(viii) NAIL

• Clean with 70 % alcohol.
• With a sterile blade, scrape away and then dispose of the outer layers of the Nail.
• Scrape bits of the inner infected nail into a sterile petridish. Transport to the lab.

(ix) SKIN

• Clean with 70 % alcohol to remove surface contaminants.
• If ringworm is present, scrape the outer portions of the red ring with a sterile scalpel or the end of a microscope slide. If there is no ring, scrape the area that looks most infected.
• Place the scrapings into a sterile petridish. Transport to the lab.

(x) EAR

• Use moistened swab to remove any debris or crust from ear canal.
• Obtain sample by firmly rotating swab in outer canal.
• Refrigerate specimen for transport. Deliver to lab within 48 hours.

(xi) EYE

• Use moistened swab to remove the material from eye conjunctiva.
• Obtain sample by firmly rotating swab in eye conjunctiva.
• Refrigerate specimen for transport. Deliver to lab within 48 hours.

LABELLING OF CLINICAL SPECIMENS

·          Each sample must have a label firmly attached to the specimen container bearing the following information:

a)     Patient’s full name

b)     Patient’s address

c)     Patient’s sex

d)     Patient’s Date of Birth

e)     Hospital number

f)      Consultant Details

g)     Sample site

h)    Date and Time of collection

i)      Initials/Signature of Collector