Objectives: Cytomegalovirus (CMV) often reactivates in ulcerative colitis (UC). In diagnostics, along with immunohistochemistry (IHC) of colonic biopsies, blood CMV polymerase chain reaction (PCR) is gaining increasing application. We aimed to assess agreement between the density of infected colonic cells by IHC and the viral load in the blood by PCR.
Material and methods: We retrospectively identified patients with active UC or indeterminate colitis in whom blood CMV PCR had been performed while biopsies had been taken simultaneously. The latter were re-evaluated and the numbers of IHC-positive cells per square millimetre counted.
Results: The analyses extended to 234 sample pairs, among which there were 184 cases (78.6% of the total) in which IHC was equal to 0. The median among the remaining 50 non-zero values for IHC was 1.7 cells/mm2. PCR was equal to 0 in 192 cases (82.1%), while the median among the remaining 42 non-zero values was 4995.3 IU/ml. The Spearman correlation coefficient was 0.43 (p < .001). The area under the curve (AUC) values did not differ significantly between different IHC cut-offs. The highest AUC of 0.753 was obtained while predicting if IHC would be above the 3rd quartile (>5.6 cells/mm2), where PCR > 0 had a sensitivity of 0.615 and a specificity of 0.846.
Conclusions: In active CMV colitis, the specificity and negative predictive value of blood PCR are high, while the sensitivity grows with the intensity of colon infection. A highly positive result could justify the administration of antiviral treatment being brought forward in selected patients.
Keywords: Ulcerative colitis; cytomegalovirus; histopathology; immunohistochemistry; polymerase chain reaction.