Field study assessing the performance of a patient-side blood test to determine neuter status in female cats based on detection of luteinising hormone

The aim of this study was to assess the performance of a patient-side blood test in determining neuter status in female cats. Residual blood samples from female cats of unknown neuter status that were admitted to four cat adoption centres in the UK were tested for luteinising hormone (LH) using the Witness LH test (Zoetis). A positive LH test result indicated that the cat was neutered. Cats were assessed for evidence of a surgical scar suggestive of prior neutering; if none was found, an exploratory laparotomy was performed to confirm neuter status. The LH test performance was assessed (sensitivity, specificity, negative and positive predictive value). Two hundred and thirty-six cats had both LH test and exploratory laparotomy data. The specificity of the test in detecting neutered cats was 100% (95% confidence interval 96.2–99.9) and the sensitivity was 69% (95% confidence interval 59.3–76.8). The prevalence of neutered cats in this sample was 49%. The positive and negative predictive values were 1 and 0.77, respectively. The Witness LH test correctly detected all unneutered cats and thus there were no false-positive results that incorrectly indicated a cat was neutered. This study therefore suggests that positive LH test results avoid the need to perform surgery to confirm neuter status. This has significant welfare benefits for cats as it provides a lower risk, faster and less traumatic alternative to surgery and, in the shelter setting, it will have a positive impact on the cost, speed of assessment and time to rehoming of cats.