Calretinin immunohistochemistry versus improvised rapid Acetylcholinesterase histochemistry in the evaluation of colorectal biopsies for Hirschsprung disease.

BACKGROUND: Acetylcholinesterase (AChE) histochemistry on rectal mucosal biopsies accurately diagnoses Hirschsprung disease (HD), but is not widely employed as it requires special tissue handling and pathologist expertise. Calretinin immunohistochemistry (IHC) has been reported to be comparable to AChE staining with the loss of expression correlating with aganglionosis. AIM: The aim was to evaluate calretinin IHC as a primary diagnostic tool in comparison to the improvised rapid AChE technique in the diagnosis of HD. MATERIALS AND METHODS: A total of 74 rectal biopsies (18 fresh frozen - 18 cases, 56 formalin fixed - 33 cases) from 51 cases of suspect HD were evaluated with hematoxylin and eosin/AChE/Calretinin. Ten biopsies each from ganglionated and aganglionated segments served as positive and negative controls. Ileal (3), appendiceal (3) and ring bowel (2) biopsies were also included. Two pathologists blinded to the clinical details evaluated the histomorphology with AChE and calretinin. Observations were statistically analyzed and Cohen's k coefficient employed to assess agreement between two pathologists and calretinin and the AChE. RESULTS: The study confirmed HD in 26 and non-HD in 25 cases. There were 7 neonates, 5 low level biopsies and 14 "inadequate" biopsies. The results of calretinin were comparable with AChE with a statistically significant measure of agreement of k = 0.973 between the two. One false-positive case of HD was noted with calretinin. The advantages and disadvantages of calretinin versus AChE are discussed. CONCLUSION: Calretinin is a reliable single immune marker for ruling out HD by its specific positive mucosal staining of formalin fixed rectal biopsy. The improvised AChE staining remains indispensable to confirm HD on fresh biopsies and thus, along with calretinin IHC maximizes the diagnostic accuracy of HD in difficult cases.