Observer variation in the assessment of the histopathologic diagnosis of acute appendicitis

Background: The objectives of this study were to determine observer variati on in the assessment of the histopathologic diagnosis of acute appendicitis . Methods: Two consultant pathologists independently evaluated 415 appendec tomy specimens (set I). After a consensus conference at which the observers unified the criteria of the diagnosis of acute appendicitis, another 396 a ppendectomy specimens (set II) were evaluated. To calculate the intra-obser ver variation, one observer evaluated set II once more. Finally, using the consensus diagnosis as the final diagnosis, the diagnostic accuracy of the surgeon, the primary pathology report, and the two observer evaluations was calculated. Results: In set I no difference was found in the level of agre ement on the diagnosis of acute appendicitis versus other diagnoses, and ai r, value of 0.85 was obtained. In set II a kappa value of 0.88 was obtained , which was not significantly different from the kappa value in set I. Howe ver, the consensus conference did increase the level of agreement on the di agnosis of acute appendicitis. The intra-observer variation was calculated, and a kappa value of 0.88 was obtained. The cases in which the observers d isagreed on a positive diagnosis were cases of mild appendicitis. The quest ion remains how many specimens would have shown these changes if all tissue had been developed for microscopy. The observers' diagnoses were the most reliable, and there was a significant decrease in the diagnostic accuracy c ompared with both the primary pathology report and the surgeon's opinion, t he last one being the least accurate. Conclusions: These observations stres s how important it is for the pathologist to discuss the diagnostic criteri a of the diagnosis of acute appendicitis and for the surgeon to go back to the patient's record and look up the histopathologic diagnosis.