Discrepancies in the determination of sperm concentration using Bürker-Türk, Thoma and Makler counting chambers.

Determination of sperm concentration by use of a haemocytometer or counting chamber is an important step in semen evaluation and is also used for calibration or validation of instruments. Three experiments were carried out to determine the precision and accuracy of the Makler chamber, the Thoma haemocytometers (50 and 100 microm deep, TH-50, TH-100) and the Bürker-Türk (BT) haemocytometer. The first experiment confirmed that precision in sperm count by use of the haemocytometers (TH-50 and BT) can be increased if a higher number of sperm are counted. In contrast, the precision of the Makler chamber was relatively unaffected by the number of sperm counted and the coefficient of variation for this chamber was significantly (P < 0.05) higher than for the two haemocytometers. Experiment 2 confirmed the low precision of the Makler chamber and also showed that the TH-50 haemocytometer underestimated sperm concentration by approximately 25% in comparison to the Makler chamber and the BT haemocytometer. Experiment 3 demonstrated a slight underestimation of sperm count by the TH-100 haemocytometer in comparison to the BT haemocytometer, but both haemocytometers yielded acceptable precision (coefficients of variation were 10.4% and 9.4%, respectively). In comparison, the precision of the Makler chamber was significantly poorer (coefficient of variation 18.6%). When used for validation of a flow cytometric method which determines sperm concentration, the Makler chamber caused a higher degree of scattering of the points around the regression line than when the flow cytometric method was validated against the BT haemocytometer. It thus appears that the poor precision of the Makler chamber also affects the accuracy. It is concluded that duplicate counts by at least two technicians is recommended to achieve high precision but, that particular caution should be exerted with regard to the precision and accuracy of the used counting device.