Colorimetric leukocyte adherence inhibition assay: a new auxiliary technique for the diagnosis of schistosomiasis.

We describe a modification of the leukocyte adherence inhibition assay (LAI) in which we propose the use of 3-(4,5-dimethylthiazole-2-yl)-2-5-diphenyltetrazolium bromide (MTT) dye which is taken up and reduced by mitochondria. The method was tested by screening peripheral blood leukocytes from Schistosoma mansoni-infected patients. Peripheral blood leukocytes from patients (N = 21) but not from the blood of normal subjects (N = 10) failed to adhere to glass in the presence of soluble adult worm antigenic preparation (SWAP). The non-adherence index (NAI) values for schistosomiasis patients were in the range of 11.0 to 72.3 (mean +/- SEM = 29.3 +/- 4.3), whereas the values for normal subjects were -56.0 to +2.0 (-25.9 +/- 7.6) and those for treated patients -59.6 to +4.0 (-19.3 +/- 5.8). Our results show that the colorimetric LAI assay can be used as an auxiliary test for the diagnosis of schistosomiasis.