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The two present studies of my thesis were performed to evaluate 1) the visual assessment of vaginal discharge by vaginoscopy and 2) the manual assessment of cervical diameter through palpation in dairy cows. Both studies are based on an in vivo and in vitro trial.
In the first study Holstein-Friesian cows (n = 380) were examined by vaginoscope between 21 and 27 days in milk by three investigators twice. Vaginal discharge was categorized on a 4-point classification system (0 = clear mucus, 1 = mucus containing flecks of pus, 2 = discharge containing less than 50 percent pus, 3 = discharge containing more than 50 percent pus). Cows with a vaginal discharge score of 0 were classified as healthy whereas cows with a vaginal discharge score of 1 to 3 were classified as having a clinical endometritis. My results illustrate that vaginal discharge score on a scale from 0 to 3 has moderate intra- (Cohen´s kappa coefficient = К; К = 0.55 – 0.60) and interobserver (К = 0.44) repeatability. The prevalence of clinical endometritis was comparable between the three investigators (1st VE: 42.6%, 34.8%, 38.7%; 2nd VE: 46.8%, 36.9%, 43.7%). Transrectal palpation (RR = 0.96 - 1.03) or experience of the investigator (RR = 0.9 - 1.1) did not affect results of vaginoscopic examination (VE). In an in vitro trial sensitivity and specificity of a visual assessment were determined utilizing 33 images showing yellow and pink areas in certain percentages as a reference standard.
Pus was represented as yellow and the mucosa including clear mucus as pink areas.
These images were visually assessed by 30 investigators via power point (experiment 1) and by 23 investigators via a simulated vaginoscopic examination (experiment 2) utilizing the same 4-point classification system. Sensitivity was 99.6% and 96.3% and specificity was 96.7% and 90.1% in experiment 1 and 2, respectively. In the second study, three investigators examined 64 Holstein- Friesian cows between 2 and 5 days in milk and between 21 and 27 days in milk by transrectal palpation. For calculation of sensitivity and specificity, ultrasound-generated measurements were used as reference standard. A cervix >7.5 cm was categorized as large. The Pearson coefficient of correlation between the results of the 3 investigators and ultrasound-generated measurements was moderate (r = 0.71, 0.74 and 0.51). The estimates generated by palpation by the 3 different investigators did not differ and were similar to measurements obtained by ultrasound.
The coefficient of variation between the investigators and ultrasound was high (20.9, 18.7 and 32.0%). The mean difference between the investigators and the ultrasound was 0.60 cm (95% confidence interval: −2.4 to 3.6 cm). Sensitivity was 28.6%, 42.9% and 42.9% and specificity was 100%, 96.2% and 92.6% for the ability of the 3 investigators, respectively, to detect a cervix with a diameter of 7.5 cm by palpation.
Overall, sensitivity and specificity for all 3 investigators, considering ultrasound measurements as reference, were 37.5% and 96.2%, respectively. In vitro, 24 wooden cylinders were used to represent cervical diameter and to examine the reliability, as well as sensitivity and specificity, of manual assessment of different diameters. The Pearson coefficient of correlation between the results of the investigators (n = 11) and the actual diameters of the cylinders was 0.78. The coefficient of variation between the investigators and the cylinders was 27.8%. The variation in the results was greater for cylinders with a larger diameter (3.5 cm diameter: mean ± standard deviation = 2.6 ± 0.9 cm; 10.5 cm diameter: mean ± standard deviation = 13.2 ± 4.0 cm). The estimate obtained by palpation for the 7.5 cm cylinder was 7.4 ± 2.1 cm. Sensitivity was 79.4 % and specificity 92.5%. After training one group of investigators, sensitivity and specificity improved to 85.9% and 94.4%, respectively. The results show that a visual assessment conducted by vaginoscopic examination is not perfect but can be considered a reasonable measurement of vaginal discharge and as a practical tool to distinguish healthy from diseased cows. My data provide clear evidence that manual assessment of diameters by palpation remains a challenge.