Tubular dysfunction in stable adult sickle cell patients in Kinshasa: prevalence and associated factors - a cross-sectional study

Renal complications of sickle cell disease (SCD) often begin with tubular dysfunction (TD), yet this entity remains insufficiently recognized in African populations. Data from adults in Kinshasa are particularly scarce. We conducted a cross-sectional study between March 2023 and April 2024, enrolling 279 clinically stable adult SCD patients from 14 centers in Kinshasa. Tubulopathy was defined by the concomitant presence of three abnormalities: urinary α1-microglobulin-to-creatinine ratio (A1M/Cr) ≥20 mg/g, dipstick glucosuria ≥1+ with plasma glucose <126 mg/dL, and urine pH ≥5.5. Glomerular involvement was assessed by urinary albumin to creatinine ratio (UACR ≥30 mg/g). Measured GFR (mGFR) was obtained by iohexol clearance. Multivariable logistic regression was used to identify independent factors associated with tubulopathy. Tubulopathy was identified in 58 patients (20.8%). Compared with those without tubulopathy, affected patients had significantly higher median A1M/Cr (44.7 vs. 14.2 mg/g; p < 0.001) and UACR (22.1 vs. 10.7 mg/g; p = 0.007). They also displayed lower mean eGFR by CKD-EPIcrea+cys2021 (107.4 vs. 115.9 mL/min/1.73 m²; p = 0.031) and higher LDH levels (217.0 vs. 209.1 IU/L; p = 0.016). In multivariable analysis, independent predictors of tubulopathy included higher LDH (per 100 IU/L increase) (aOR 2.53, 95% CI 1.14–5.61), UACR ≥30 mg/g (aOR 1.94, 95% CI 1.18–5.18), while hydroxyurea use was independently associated with lower odds of tubulopathy (aOR 0.37, 95% CI 0.16–0.87). One in five stable adult SCD patients in Kinshasa presented with tubulopathy. This phenotype was associated with hemolysis, albuminuria, and lower eGFR, whereas hydroxyurea use was inversely associated with tubulopathy.