Purpose: To suggest a method for evaluating the accuracy of different kinds of sperm counting chambers by eliminating errors concerned with human skills or semen properties. In this method, various concentrations were prepared from stocks of commercially available latex beads (Accu-beads, Hamilton-Thorn Research, Beverly, MA). Samples from identical preparations were loaded into different types of chambers, namely, hemocytometer (Neubauer, improved double, Superior Ltd, Germany), Makler (Sefi Medical Instruments, Haifa, Israel) and Horwell (Horwell Ltd, London, UK). Beads were counted by both direct microscopic observations and by strict scanning of their photographed images.
Results: In all cases, counts by direct observation were about 5% higher than strict counts of the same photographed beads. Counting photographed beads showed high reproducibility (average CV of 5.1%) between samples in the two wells of the hemocytometer. Counts of photographed beads, sampled from identical stocks, were on average slightly lower in the Makler chamber (20.7 x 10(6)/ml) and much higher in the Horwell chamber (47.4 x 10(6)/ml) than counts in the hemocytometer (21.5 x 10(6)/ml). Samples from three different batches of Accubeads revealed slight variation in counts between the batches and an average concentration of 11% above the number indicated on the commercial product. CONCLUSIONS; A technique that combined loading latex beads from identical stock into various chambers, proper covering of the tested samples and strict counting of photographed beads provided precise and reproducible results. By eliminating most errors related to human skills and semen properties, this method is suitable for evaluating the accuracy of counting chambers.