A. Background information
Thick smears consist of a thick layer of dehemoglobinized (lysed) red blood cells
(RBCs). The blood elements (including parasites, if any) are more concentrated
(app. 30×) than in an equal area of a thin smear. Thus, thick smears allow a more efficient detection of parasites (increased sensitivity). However, they do not permit an optimal review of parasite morphology. For example, they are often not adequate for species identification of malaria parasites. If the thick smear is positive for malaria parasites, the thin smear should be used for species identification.
B. Preparation of malaria thick smear from a finger stick
1. Identify the survey participant.
2. Place all collection materials on top of disposable pad. Place the correct label on the rough frosted end of the slide. At a minimum, the label should indicate the sample ID and collection date. Once the patient is seated comfortably, open the lancet, alcohol swabs, gauze, bandage, and other items. Have all items ready for blood collection.
3. Put on your powder-f ree gloves. Turn patient’s hand upward. Massage patient’s hand and lower part of the finger to increase blood flow.
4. Scrub the patient’s middle finger or ring finger with an alcohol swab. Dry with gauze.
5. Hold the finger in an upward position and lance the palm side surface of the finger between the nail and the finger pad with the proper size lancet
(adult/child). Press firmly on the finger when making the puncture. Doing so will help you to obtain the amount of blood you need. Immediately discard the lancet into the sharps container.
6. Using a dry gauze pad, wipe away the first drop of blood. Next, touch the clean, labeled microscope slide near one end to the second formed blood drop. Make sure that blood drop is placed on same side of the slide that the label is on.
Always grasp the slide by its edges.
7. Spread the drop of blood with the corner of another slide or an applicator stick to make an area about 1 - 1.5 cm in diameter. Correct thickness is attained when newsprint is barely legible through the smear.
8. Apply a sterile adhesive bandage over the puncture site.
9. Lay the slides flat and allow the smears to dry thoroughly. Protect the slides from dust and insects. Insufficiently dried smears and/or smears that are too thick can detach from the slides during staining. This risk is increased in smears made with anticoagulated blood.
At room temperature, drying can take several hours; 30 minutes is the minimum.
Handle the smear very delicately during staining. Protect thick smears from hot environments to prevent heat-fixing the smear.
C.
Preparation of malaria thick smear from venous blood
If you are using venous blood, blood smears should be prepared as soon as possible

after collection. A delay can result in changes in parasite morphology and staining characteristics.