Laboratory and Clinical Evaluation of a Feia Method for Canine Serum Progesterone Assay

The evaluation of progesterone (P4) concentration is a valuable tool in assessing physiological reproductive events and reproductive disorders in bitches. A reliable and rapid (preferable, point of care) determination of P4 is advisable in most cases. Aims of this study were to evaluate a fluorescence enzyme immunoassay (FEIA) for canine serum P4 concentration by (i) the agreement with liquid chromatography-tandem mass spectrometry (LC/MS/MS), (ii) the association with vaginal cytology and (iii) the accuracy in the prediction of the parturition date calculated from the estimated day of ovulation. Serum samples were collected from client-owned bitches presented between 2011 and 2014 for the evaluation of their oestrous cycle, pregnancy or reproductive disorders. The agreement between FEIA and LC/MS/MS, evaluated on 19 samples, was statistically significant (R(2) = 95.7%, p < 0.001), although FEIA showed significantly higher values than LC/MS/MS (p < 0.05). In the different phases of oestrous cycle, as determined by vaginal cytology, P4 concentrations (by FEIA) were statistically different (p < 0.05): anoestrus (n = 7) 0.38 ± 0.14 ng/ml, proestrus (n = 14) 1.04 ± 0.67 ng/ml and oestrus (n = 72) 6.8 ± 7.26 ng/ml. Mean pregnancy length from the estimated day of ovulation was 62.9 ± 1.8 days. In 13 of 22 (59.1%), 19 of 22 (86.3%) and 21 of 22 (95.5%) bitches pregnancy lasted 63 ± 1, 63 ± 2 and 63 ± 3 days, respectively. Three pregnancies were outside the 61-65 days range (60, 60 and 67 days). In conclusion, the FEIA method employed can be considered reliable and, in association with vaginal cytology, effective in evaluating the canine oestrous cycle.