Value of counting white blood cells (WBC) in semen samples to predict the presence of bacteria.

Objectives: To investigate the correlation between the presence of white blood cells (WBC) without the use of specific stain to differentiate leukocytes and the presence of bacteria in semen samples of infertile men.
Methods: A total of 143 semen samples of men who attended an andrologic clinic for the evaluation of fertility were investigated using routine semen analysis (according to WHO laboratory guidelines) and bacterial culture.
Results: WBC were found in 43.4% (62/143). There were no WBC in 56.6% (81/143) of the samples (group I) while WBC were found in 43.4% (62/143) of the samples (group II). Pathogenic bacteria were detected in 48.2% (39/81) in group I and in 54.9% (34/62) in group II, all in all Bacteriospermia was present in 51.1% (73/143). The most common bacteria were Ureaplasma urealyticum, Enterococcus faecalis and Escherichia coli (23.8%, 16.8%, and 7.0% of samples, respectively). The sensitivity/specificity for detecting bacteria was 0.47/0.60 at a cut-off level of 0.25 Mio/mL WBC and 0.16/0.84 at a cut-off level of WBC 1 Mio/mL, representing likelihood ratios of 1.16 and 1.04, respectively. The greatest ratio between sensitivity and specificity (0.37/0.72) was found at a cut-off level of 0.5 Mio/mL WBC, with a likelihood ratio of 1.29.
Conclusions: Counting WBC instead of a specific stain for the detection of leukocytes has only a poor sensitivity/specificity for the detection of bacteria.