RESUMO
The resazurin reduction test (RRT) was performed on semen samples obtained from 225 untreated subfertile and 10 pregnancy confirmed fertile males. The results of RRT were determined visually using resazurin colour chart and again the extent of resazurin reduction in each sample was additionally read by spectrophotometer to assess the quality of samples. Absorption spectra was scanned for resazurin and resorufin and two most sensitive wavelengths (572 and 600 nm) were selected. The ratio of the two optical densities was used as a probe to discriminate the various grades of semen samples. In azoospermic samples, RRT ratio ranges from 0.7 to 1.16, in oligoasthenozoospermic samples from 1.10 to 1.35, in oligozoospermic samples from 1.5 to 2.0 (characterised visually as grades from 1-4) in normozoospermic and proven fertile samples from 2.25 to 5.9 (characterized visually as grades from 5 to 11). The highest correlation of RRT ratio was observed with sperm motility (r = 0.889, P < 0.001), followed by concentration (r = 0.848, P < 0.001) morphology (r = 0.660, P < 0.001) and viability (r = 0.544, P < 0.01). The test ratio had a positive predictive value of 95% for a sperm concentration of > 20 x 10(6)/ml and motility > 40% and a negative predictive value of 90% for a sperm concentration of < 20 x 10(6)/ml and motility < 40%. Therefore the evaluation of RRT results using spectrophotometric ratio method may provide a tool for obtaining a wider range of seminological diagnosis more accurately than the routine semen analysis. It is suggested that the method is simple and reliable, it can be performed in any andrology laboratories.