Histopathological Diagnosis of Leprosy Type 1 Reaction with Emphasis on Interobserver Variation.

Upgrading typel lepra reaction or reversal reaction (RR) is an acute inflammatory complication of leprosy and a disparity exists between clinicians and pathologists for diagnosing a RR. Inter-observer variations among pathologists also compound this problem as no universally agreed diagnostic criteria exist. 120 biopsies and H&E stained slides were assessed by 3 pathologists. The pathologists were blinded to the clinical diagnosis and to each other's observations. Each pathologist assigned a likelihood of reaction by their histopathological observations as definitely reaction, probable reaction and no reaction. Clinicopathological correlation and interobserver agreement was analyzed statistically. Discordance between clinical and histopathological diagnosis was seen in 30.8% by pathologist 1 (P1), 23.7% by pathologist 2 (P2) and 34.5% bythe pathologist 3 (P3). Dermal edema, intragranuloma edema and epidermal erosion were consistent findings by all observers. Definite reaction was seen in 54.2% of cases by P1, 53.3% by P2 and 34.5% by P3. Kappa statistics for strength of agreement showed good agreement between 3 pathologists with P1 (κ = 0.83), P2 (κ = 0.61), P3 (κ = 0.62). RR are underdiagnosed on histopathological examination but this study shows that dermal edema, edema within the granuloma and partial obliteration of grenz zone by granuloma are reliable clues to diagnose a RR on histopathology.