The validation of the Helicobacter pylori CagA typing by immunohistochemistry: nationwide application in Indonesia

We aimed to validate 2 types of antibodies, anti-CagA antibody and anti-East Asian CagA specific antibody (α-
EAS antibody) for the determination of CagA status in Indonesia. We also confirmed the performance of α-EAS
antibody for the detection of East Asian-type CagA H. pylori. Immunohistochemistry was performed using anti-
CagA antibody and α-EAS antibody on gastric biopsy specimens from a total of 967 Indonesian patients.
Diagnostic values of immunohistochemistry were evaluated with PCR-based sequencing as gold standard. Anti-
CagA antibody had high sensitivity, specificity, and accuracy (87.0 %, 100 %, and 98.8 %, respectively) for
determining CagA status. The α-EAS antibody was not suitable for the purpose of CagA status determination, as
it had a low sensitivity (23.9 %). High specificity (97.6 %) but low sensitivity (41.2 %) and accuracy (66.3 %)
was observed in α-EAS antibody to detect East Asian-type CagA. Patients with positive result of im-
munohistochemistry using anti-CagA antibody had significantly higher monocyte infiltration score in antrum
(P< 0.001) and corpus (P = 0.009). In conclusion, the anti-CagA antibody is still suitable to be used in
Indonesia for determining the CagA status, whilst the α-EAS antibody was not appropriate to discriminate be-
tween East Asian-type and non-East Asian-type CagA in Indonesia.