The relationship between the pretreatment hemoglobin and the platelet increase after anti-D was evaluated in HIV⁻ (A) and HIV⁺ (B) adults. Patients with low baseline hemoglobin (<12 g/dL) were compared with those with normal values (≥12 g/dL). The x-axis depicts baseline hemoglobin values; the y-axis shows the platelet increases after anti-D treatment. Significantly higher platelet increases were seen in the adult patients with normal pretreatment hemoglobin (P = .0002). The influence was stronger in the HIV⁺ patients (P < .01) than in the HIV⁻ ones (P = .084). *One HIV⁺ adult patient was excluded from the analysis; the baseline hemoglobin was 9.2 g/dL, but the platelet increase after anti-D (327 × 10³/μL) was out of the range of the entire adult group.