This study is a cross sectional hospital-based study held in Omdurman Military Hospital, which is the one of the biggest tertiary hospitals in the Sudan. A total sample of 32 SCA adult patients (13 males, 19 females) in a steady state, who attended the hematology referred clinic in the hospital from October to December 2017. Control group (11 males, 12 females) were healthy students recruited from Faculty of Medicine, Al Neelain University. Diabetics, Chronic Kidney Disease (CKD) patients due to other causes, patients with acute illness and pregnant women were excluded.
Blood pressure (BP) measured for all participants using mercury sphygmomanometer and stethoscope. Participants were classified according to the last American Heart Association classification of hypertension in to: normal BP, elevated BP, stage 1 and stage 2 hypertension; if their BP ˂ 120/80, 120–129/80, 130–140 /80–90 and > 140/90 respectively (9). Weight was measured in Kilogram using digital weight scale. Height was measured by meter using wall mounted scale. BMI was calculated from the height and weight using this equation: BMI = Weight in Kg/ (height in meter) 2
Patients were classified according to the WHO classification of BMI available at (http://apps.who.int/bmi/index) to underweight, obese, overweight and normal weight when their BMI: < 18.5, ˃30, 24.9–30, 18.5–25 Kg/m2 respectively.
Venous blood sample (5 ml) was obtained from each participant in to plain, EDITA and heparin containers. Then the collected samples sent to the laboratory for CBC, RFT, UA, bilirubin and reticulocyte count using Automated Hematology Analyzer (BC-2800 Mindary, Nanshan, China). Random spot urine collected in clean, dry, closed, wide neck urine container and sent to the laboratory for PCR using colorimetric method. Study population classified according to their PCR using NICE Guidelines to group with significant proteinuria if PCR ≥ 50 mg/mmol and another with non-significant proteinuria when PCR ˂ 50 mg/mmol (10).
GFR calculated using CKD-EPI formula without adjustment for ethnicity which is the best GFR formula for SCD (11). This formula was proved by France prospective observational cohort study conducted in Sub-Saharan and French West Indies native populations; after the comparison between measured GFR using Iohexol plasma clearance method with estimated GFR by using formulas (MDRD, Cockcroft-Gault, CKD-EPI, CKD-EPI and MDRD without adjustment for ethnicity)(11). GFR < 60 ml/min/1.73 m2 regarded as CKD. Despite there is no consensus about the cut-off point of hyper-filtration; more than 130 ml/min/1.73 m2 in females and > 140 in males is regarded as glomerular hyper-filtration based on previous reported literature(12).
CKD-EPI without adjustment of ethnicity formula:
GFR (ml/min/1.73 m2) = 141 min (Scr/k, 1) α× max (Scr/k, 1)−1.209×0.993age × 1.018 (if female).Whereas: SCr is Serum Creatinine, k is 0.7 for females and 0.9 for males, α is -0.329 for females and − 0.411 for males, min: indicates the minimum of SCr/k or 1, and max indicates the maximum of S. Cr/k or 1.
Severity score is estimation of risk of death among SCD was calculated using a validated online clinical severity score calculator based on study made by Sebastian et al(13) and developed by Bioinformatics group called Bios in the University of Granada in Spain and made it available freely online at http:/bios.ugr.es/dss-calculator. Severity score includes clinical and laboratory characteristics to estimate 5-year-risk of death among sickle cell anaemia patients. The range of the score is from zero to one; where zero means 0% and one means 100% risk of death in the next five years. Fifteen out of sixteen clinical and laboratory characteristics were entered to the online calculator. Severity Score Variables include: Stroke, blood transfusion times, pain, priapism, acute coronary syndrome, avascular necrosis, systolic blood pressure, Hemoglobin, Hb genotype, MCV, TWBCs, Reticulocyte count, and Serum bilirubin beside age and gender. Patients were classified in to high, moderate and low risk of death if they score > 0.72, (0.55–0.72) and < 0.55 respectively according to Guilhreme et al study(14).
Data were summarized and analysed using (SPSS) version 23. We used frequency tables, means and standard deviation (SD) to describe the values. One-sample Kolmogorov-Smirnov Test was used to test the distributions of variables. Unpaired T. Test was used for normally distributed variables and Mann Whitney U test for non-normally distributed ones. A correlation analysis was applied to investigate the relation between study variables. p- value ˂ 0.05 was considered as statistically significant cut off point.
Study was ethically approved from Institutional Review Board (IRB) of Al Neelain University. Informed written consents were obtained from participants after explaining the purpose, procedures and measurement needed for the study.