Intra- and inter-observer agreement when using a descriptive classification scale for clinical assessment of faecal consistency in growing pigs

The objective of the current study was to evaluate intra- and inter-observer agreement using a descriptive classification scale with four categories, descriptive text and pictures for assessment of consistency in faecal samples from pigs post weaning. The four consistency categories were score one = firm and shaped, score two = soft and shaped, score three = loose and score four = watery.

Five observers from the same veterinary practice examined 100 faecal samples using the scale with four categories. Four of the observers examined the 100 faecal samples twice within the same day.

Within observers the difference in proportions for the individual consistency categories between two examinations was on average 0.04 (range: 0–0.10). The mean intra-observer agreement was 0.82 (range: 0.72–0.91) with a mean kappa value of 0.76 (range: 0.61–0.88).

For inter-observer agreement overall kappa was 0.64. For the 10 pair-wise comparisons the mean inter-observer agreement was 0.73 (range: 0.61–0.90) with a mean kappa value of 0.64 (range: 0.48–0.87). The difference in proportions for the individual consistency categories was on average 0.08 (range: 0–0.17).

In conclusion, the agreement observed for the descriptive classification scale with four categories, descriptive text and pictures may be categorized as a substantial to almost perfect intra-observer agreement and a moderate to almost perfect inter-observer agreement.

However, more objective measures than clinical scales may still be needed to improve intra- and inter-observer agreement in research studies.