Total Antioxidant Capacity in beta-thalassemia: A systematic review and meta-analysis of case-control studies

- Total Antioxidant Capacity (TAC) is decreased in thalassemics versus healthy subjects.
- Similar decreased TAC levels were found in beta-thalassemia major and trait.
- No relationship between TAC and disease severity could be established.
- The possible interference of uric acid and bilirubin must be taken into account.
- Uric acid-independent TAC might be the better approach to evaluate antioxidant status.

Total Antioxidant Capacity (TAC), a biomarker measuring the antioxidant potential of body fluids, including redox synergistic interactions, is influenced by the presence of products of catabolism such as bilirubin (BR) and uric acid (UA). Hyperuricaemia and increased BR levels were observed in thalassemia. In order to evaluate the differences in TAC values between thalassemic patients and healthy subjects, we performed a systematic review and meta-analysis of case-control studies. After the exclusion of data deemed unsuitable for meta-analysis inclusion and a study imputed of bias by Trim-and-fill analysis, mean difference (MD) and confidence intervals 95% (CI 95%) were calculated by the random effect model for beta-thalassemia major (BTM) (1351 subjects: 770 thalassemic and 581 controls, from 15 studies) and Trait (BTT) or Hemoglobin E (BTE) (475 subjects: 165 thalassemic and 310 controls, from 5 studies). Despite the differences in clinical symptoms and severity, similar decreased levels of TAC were found in BTM [MD −0.22 (−0.35 −0.09) p < 0.001] and BTT or BTE [MD −0.22 (−0.44 −0.01) p < 0.05]. In conclusion, UA and BR interference on TAC suggests that corrected TAC and in particular the UA-independent TAC, considering the prominent influence of UA, might be the better approach to evaluate body antioxidant status.