Quality assurance of canine vaginal cytology: a preliminary study

Regulatory controls of quality assurance in veterinary laboratories are less common than in human reproduction laboratories and the intra- and inter-technician variation in the assessment of canine vaginal cytology has not been reported. This study was designed to determine whether variation in classification of vaginal epithelial cells and interpretation of vaginal cytology smears existed within and between technicians in a canine reproductive laboratory. Sixteen vaginal cytology smears representing different known stages of the oestrous cycle were examined twice by one experienced technician and three inexperienced technicians in a blinded random order study design. Seven assessments were made; counting and classifying one hundred vaginal epithelial cells into four morphological classifications and assessment of three cellular categories. Technicians also interpreted their results and reported the stage of the cycle they thought each slide represented. In addition, selected samples were sent to four external commercial laboratories for interpretation. For the experienced technician, intra-technician variation was low for the morphological classifications and cellular assessments (r = 0.69-0.95). There was more intra-technician variation between results from Examination One and Examination Two for the inexperienced technicians (r = 0.53-0.92 where correlations were found). When inexperienced technicians' results were compared to results from the experienced technician, the inter-technician variation was low; results were correlated for 17 of the 21 observations (four morphological classifications and three cellular assessments across the three technicians) (r = 0.38-0.87). When technician interpretations of stage of the oestrous cycle were compared to the known stage of the cycle for each smear, the experienced technician correctly interpreted 19 of the 32 smears, whilst the three inexperienced technicians correctly interpreted 14, 16, and 18 of the 32 smears. The interpretation of vaginal smears by external laboratories was varied and sometimes inconclusive; 50% of laboratories incorrectly identified metoestrus smears as proestrus and 25% of the laboratories incorrectly identified an oestrus smear as proestrus. The results of this study are highly important for clinicians undertaking canine reproductive assessments since they demonstrate the potential for variability of results. While the greatest precision was found when vaginal smears were examined by an experienced technician (who, on a daily basis, examines many smears), more variability in both the reporting of different cell types and interpretation of the smears was observed by inexperienced technicians and when samples were sent to external commercial laboratories. These findings suggest that suitable quality control programmes should be implemented for laboratories that are undertaking routine assessments of canine reproductive function.