Evaluation of the blood progesterone concentration in the bitch measured by chemiluminescence immunoassay at the day of ovulation

Objective: Modifications of human test systems used in veterinary laboratory practice could lead to reference-range adaptions for their veterinary use. In 2012 the manufacturer of a widely used chemiluminescence immunoassay modified the test for progesterone measurement leading to a reference range adaption for the breeding-time detection in the bitch. Material and methods: The aim of the present study was to evaluate the mean progesterone concentration by using the modified chemiluminescence immunoassay at the time of ovulation in the bitch and to compare this with previously used reference ranges. Moreover, internal and external quality controls were per formed and progesterone concentrations measured in different laboratories with different methods were compared at a national and international level. Results: In the present study, it could be demonstrated that the concentration of progesterone of 0-6 ng/ml measured by the modified test was clearly lower than that measured by the previously delivered test. National and international quality control assurance showed a good agreement of progesterone measurements between different laboratories and with the modified test. In seven bitches, the mean progesterone concentration on the day of ultrasono-graphically detected ovulation was 3.4 +/- 0.9 ng/ml (2.0-4.5 ng/ml). Conclusion: This analysis indicates the need to change the widely accepted reference value for ovulation from 5-8 ng/ml to similar to 3.5 ng/ml for the currently used method. Particularly in veterinary endocrinology, the routine evaluation of reference values should be standard for good laboratory practice. However, the respective reference range is laboratory specific.