Assessment of diagnostic accuracy of Gazelle: A point-of-care testing device for screening β-thalassemia trait

Background & objectives: Timely detection of population with beta-thalassemia trait (BTT) followed by genetic counselling is an advocated method of preventing the birth of a child with beta-thalassemia major. In this study we aim to assess the diagnostic accuracy of Gazelle, a point-of-care (POC) testing device, in screening for BTT in hospital laboratory setting. Methods: Standards for Reporting Diagnostic Accuracy (STARD) guidelines were followed in developing study design, recruiting study participants and sample size calculation for the current research. A consecutive sample of 446 participants was recruited for this study and was tested for the reference test Gazelle as well as the gold standard cation exchange high performance liquid chromatography (CE-HPLC). Low serum ferritin levels are known to interfere with the production of HbA2 and in turn lead to false negative results. Hence, the study population was divided into two categories with respect to a cut off value of 15ng/dl of serum ferritin and the results were analyzed. Results: Overall diagnostic accuracy of Gazelle for detecting BTT was found to be 95.3 per cent with a confidence interval (CI) of (92.9 - 97.1) and the sensitivity was 94.5 per cent with a 95% CI of (84.8 - 98.8). When analyzed by the serum ferritin level the diagnostic accuracy was found to be 94.7 per cent (91.1% - 97.1%) and 95.7 per cent (91.8% - 98.1%) for participants with serum ferritin level as > 15 ng/ml and < 15 ng/ml, respectively. Interpretation & conclusions: This study found Gazelle to be a good screening tool for beta-thalassemia trait with high sensitivity, specificity and accuracy. However, it is recommended that the final confirmation of the diagnosis done by a diagnostic test like HPLC or Capillary Zone Electrophoresis (CZE).