Manual of basic techniques for a health laboratory - libdoc.who.int

196 Manual of basic techniques for a health laboratoryFormol gel test for visceral leishmaniasisThis test is a non-specific indicator for the increased serum levels of gamma globulinthat are seen in most patients with visceral leishmaniasis.Fig. 4.166 Leishmania spp.amastigotesMaterials and reagents●●●●●Test-tubesTest-tube rackCentrifugeCentrifuge tubesFormalin (37% formaldehyde).Method1. Collect 2–5ml of blood into a centrifuge tube and allow it to clot.2. Separate the serum by centrifuging the tube for 3 minutes at 5000g or by leavingthe tube overnight in a refrigerator or on the bench.3. Pipette 1ml of clear serum into a test-tube.4. Add two or three drops of formalin to the serum. Allow the tube to stand for 30minutes.ResultsA positive result is shown by gelling of the serum — it becomes solid and turnswhite, usually after about 5 minutes.A negative result is recorded when there is no gelling or whitening of the serum.Note: Increased gamma globulin concentrations in serum are also seen followinghepatitis B infection (see section 11.8) and in certain malignant diseases, such asmultiple myeloma and Waldenström macroglobulinaemia.