Chronic Granulomatous Disease: A Multicentre Study of DHR Flow Cytometry Results and Clinical Correlations in Malaysia

Background: Chronic granulomatous disease (CGD) is an inherited primary immunodeficiency disease that results from a defect in one of the respiratory burst oxidases (NADPH oxidase) genes that form its components. The diagnostic laboratory assessment for CGD includes evaluation of NADPH oxidase function in neutrophils, using DHR test. The main objective of this project is to develop an internal reference range by determining the relative proportion of oxidising cells percentages and the mean fluorescence intensity (MFI) for complete interpretation of the test results and more accurate results. Methods: A retrospective analysis was conducted on 107 individuals referred for DHR testing from Institut Perubatan dan Pergigian Termaju (IPPT) and Hospital Universiti Sains Malaysia (HUSM). Purposive sampling was employed. Logistic regression was used to explore relationships between groups and test parameters, and receiver operating characteristic curve (ROC) analysis assessed test precision. Results: From our findings, the optimum cut-point for IPPT to differentiate CGD patients from healthy group with fMLP% was 0.26%, and FMLP MFI was 9.15, PMA% was 58.70%, and PMA MFI was 50.00. For the HUSM data, the best possible cut-point for fMLP% was 3.86%, FMLP MFI was 999.50, PMA% was 45.69%, and PMA MFI was 1130.50. The parameters showed a good analytical ability since all the area under the curve (AUC) values were significant (P > 0.5). Conclusion: This study confirmed the importance of developing an internal reference range for accurate diagnosis of CGD. This data showed a difference between two centres in terms of test results and cut-points, highlighting the need for standardised reference ranges in diagnostic testing.