COMPARATIVE-EVALUATION OF MODIFIED TRICHROME AND UVITEX 2B STAINS FORDETECTION OF LOW NUMBERS OF MICROSPORIDIAL SPORES IN STOOL SPECIMENS

At present, the laboratory diagnosis of intestinal infections caused b y microsporidia depends on the detection of the epical spores either w ith a modified trichrome stain (MTS) or by staining with fluorochromes . The purpose of the present study was (i) to compare staining with MT S (MTS method) and the staining with the fluorochrome Uvitex 2B (U2B m ethod) with respect to their sensitivities and specificities, particul arly in the presence of low numbers of spores, and (ill to evaluate th eir reliabilities under routine laboratory conditions. First, 30 negat ive human stool specimens as well as 30 specimens enriched with a low concentration of microsporidial spores were examined, The U2B and MTS methods detected 27 and 30, of the positive samples, respectively (95% confidence intervals for sensitivity, 0.73 to 0.98 for the U2B method and 0.88 to 1.00 for the MTS method) without yielding false-positive results (95% confidence intervals far specificity, 0.88 to 1.00 for th e MTS and U2B methods). In addition, analysis of serial dilutions of 1 7 stool specimens from AIDS patients containing microsporidia revealed comparable detection thresholds (P = 0.52) for both methods. Finally, 40 slides prepared fi um one stool specimen containing very few micro sporidia and 40 negative slides were included in the routine diagnosti c program during 1 month in order to monitor laboratory handling and r un-to-run variations, Again, both methods exhibited comparable sensiti vities (95% confidence intervals, 0.83 to 0.99 for the MTS method and 0.91 to 1.00 for the U2B method) and specificities (95% confidence int ervals, 0.91 to 1.00 for the MTS and U2B methods). In conclusion, MTS and U2B methods are equally useful in the diagnosis of microsporidiosi s, However, since detection thresholds for both methods differed consi derably in all diluted stool specimens, performance of a combination o f both methods may be more sensitive than the performance of only one procedure in the event of very low numbers of microsporidial spores.