Pregnancy Diagnosis in Cats Using a Rapid, Bench-top Kit to Detect Relaxin in Urine

Relaxin is a pregnancy-specific hormone in the queen and is produced by the placenta. Both serum and urinary relaxin levels can be used to diagnose and monitor pregnancy in the cat; however, only serum levels are commonly measured in practice. The present study aimed to assess whether urine could be used for the rapid diagnosis of pregnancy at an early stage in domestic cats using a bench-top kit to detect relaxin. Paired serum and urine samples were collected during the first month of gestation in six cats. The samples were tested by applying neat serum, urine or urine diluted in non-pregnant cat serum to the Witness Relaxin kit. Relaxin concentrations in the paired samples were also measured by radioimmunoassay. All undiluted urine samples from pregnant cats tested negative using the bench-top kit; however, the kit was able to detect relaxin in urine after dilution with non-pregnant cat serum. Using this as the test sample, the kit was accurate at diagnosing pregnancy from 28 days after mating and some samples tested positive at 21 days after mating. This preliminary work could lead to the development of a home pregnancy test for cats.