Blood Specimens - Specimen Collection

Timing:

Whenever possible, specimens should be collected before treatment is initiated. When malaria and babesiosis are suspected, blood smears should be obtained and examined without delay. Since the parasitemia may fluctuate, multiple smears might be needed. These can be taken at 8 to 12 hour intervals for 2 to 3 days.

Microfilariae exhibit a marked periodicity depending on the species involved, therefore the time of specimen collection is critical. If a filarial infection is suspected, the optimal collection time for demonstrating microfilariae is:

• Loa loa—midday (10 AM to 2 PM)
• Brugia or Wuchereria—at night, after 8 PM
• Mansonella—any time
• Onchocerca—any time

Type of Sample:

Venous blood samples provide sufficient material for performing a variety of diagnostic tests, including concentration procedures (filariasis, trypanosomiasis). However, in some parasitic diseases (e.g., for diagnosis of malaria in particular), anticoagulants in the venous blood specimen can interfere with parasite morphology and staining characteristics; this problem can be further compounded by excessive delays prior to making the smears. In such cases, capillary blood samples are preferable. If PCR is required, please refer to the molecular diagnosis section for appropriate blood collection procedures.

Capillary blood obtained by fingerstick:

1. Label pre-cleaned slides (preferably frosted-end) with the patient's name (or other identifier) and date and time of collection.
2. Clean the site well with alcohol; allow to dry.
3. Prick the side of the pulp of the 3rd or 4th finger (alternate sites include ear lobe, or in infants large toe or heel).
4. Wipe away the first drop of blood with clean gauze.
5. Prepare at least 2 thick smears and 2 thin smears.

Venous blood obtained by venipuncture:

1. Label collection tubes and pre-cleaned slides (preferably frosted-end) with the patient's name (or other identifier) and date and time of collection.
2. Clean the site well with alcohol; allow to dry.
3. Collect the venous blood in a vacuum tube containing anticoagulant (preferably EDTA); alternatively, collect the blood in a syringe and transfer it to a tube with anticoagulant; mix well.
4. Prepare at least 2 thick smears and 2 thin smears as soon as possible after collection.

For additional information about blood collection, call the Division of Parasitic Diseases at (404) 718-4110.