Circulating relaxin concentrations in pregnant and nonpregnant bitches: evaluation of a new enzymeimmunoassay for determination of pregnancy.

: A new kit (ReproCHEK RELAXIN) intended for the diagnosis of pregnancy in bitches is now available for veterinary use. This assay measures relaxin concentrations in plasma and whole blood samples, and the presence of significant amounts of relaxin is indicative of pregnancy. A clinical trial was carried out to evaluate the performance of the test. Serial blood samples were collected on alternate days, and relaxin concentrations were determined from day 15 to day 35 after the LH surge (estimated by progesterone concentrations). Pregnancy was confirmed using ultrasonography. At the end of pregnancy, both the day of whelping and the size of the litter were recorded. Pregnancy was established in 61 bitches. The day that pregnancy was detected using the relaxin assay ranged from day 19 to day 28 after the LH surge and had a mean (+/- SD) of 25.4 +/- 2.5 days. The day of parturition was taken as a reference point, and pregnancy was detected from -46 to -38 days (mean -40.2 +/- 2.4 days) before parturition. False positives were not observed in pseudopregnant bitches (n = 16) or in the control group (30 anoestrous and ten unmated bitches). These results demonstrate that the new assay kit is an inexpensive, user-friendly and reliable technique for determining pregnancy.