GSTM1 and anemia: A paired t-test demonstrated a statistically significant reduction in Hb during infection (mean baseline Hb 9.62 ± 0.79 g/dL vs. nadir 5.90 ± 1.61 g/dL; t(9) = 6.82, p < 0.001), with a large effect size (Cohen’s d ≈ 2.16), confirming the clinical severity of anemia induced by B19V (Table 2).