Objective: To determine the earliest day of gestation at which relaxin could be detected in pregnant queens by use of a commercially available point-of-care test designed for use in dogs, and to calculate sensitivity and specificity of the test for pregnancy detection on any specified day of gestation.
Design: Evaluation study.
Animals: 162 female cats (24 queens from a breeding colony, 128 stray and feral queens undergoing ovariohysterectomy, and 10 ovariohysterectomized cats).
Procedures: 24 queens were monitored for pregnancy. Blood samples were collected daily and tested for relaxin until 2 consecutive positive test results were obtained. The earliest day of pregnancy detection was estimated by counting backward from the day of parturition to the day of the first positive test. The uteri, ovaries, and any fetuses of 128 stray and feral queens undergoing ovariohysterectomy were examined grossly, and gestational day in pregnant queens was determined on the basis of fetal crown-rump length. Blood samples from these queens and from 10 cats ovariohysterectomized prior to the study were collected for relaxin testing.
Results: Pregnancy was detected by use of the relaxin test kit as early as gestational day 20; sensitivity of the test was 100% on and after gestational day 29. False-positive results were detected in 3 queens, 2 of which had large (approx 2×3-cm) ovarian cysts, resulting in a specificity of 95.9%.
Conclusions and clinical relevance: A commercially available relaxin test kit designed for use in dogs can be used to reliably detect pregnancy in cats.