Study design and setting
A multistage survey was conducted in Elrikieb, East Gezira, in Central Sudan from April to June 2025. Elrikieb, one of the largest villages in East Gezira, was chosen because it comprises four sub-villages, and the inhabitants of these sub-villages could be representative of those of the entire Gezira State. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines were strictly followed [9].
Study population and sampling
Both male and female adults aged 18 years or older residing in the selected communities were recruited. Exclusion criteria included individuals who were unable to provide informed consent and those with severe cognitive impairment that precluded reliable completion of the questionnaire.
A multistage stratified random sampling approach was employed to select the participants. Within each selected sub-village, households were randomly chosen. All adults (male or female) in the selected household were enrolled; if there were no adults in the selected household, adults in the next household were enrolled.
Sample size calculation
A sample size of 767 adults was calculated based on the assumption that 10.0% of the adults would have CKD. This assumption was based on previous findings from small sample studies conducted in Khartoum and central Sudan, which showed that 10.0% of adults had CKD [7, 8]. Based on previous reports on CKD in Sudan over the years [7], we assumed that 45.0% of adults with CKD would be older than 50 years, whereas 25.0% of adults without CKD would be older than 50 years [7]. A sample size of 767 would have a power of 80% and an alpha significance level of 0.05.
Data collection
After each participant signed an informed consent form, data were collected by trained medical officers (two males and two females) using a questionnaire during face-to-face interviews. The questionnaires were developed for this study (additional file 1), and they included data on sociodemographic factors, such as age, sex, education level, marital status, employment status, smoking status, alcohol consumption, medical history (including diabetes mellitus and hypertension), and medications used, including diuretics. In cases where a history of diuretic use was indicated, participants were requested to show the medical officer the tablets/capsules for confirmation. Each participant’s weight and height were measured using standard procedures, and their body mass index (BMI) was calculated as weight in kilograms divided by the square of their height in meters. The participants were then grouped according to the World Health Organization classification: underweight (< 18.5 kg/m²), normal weight (18.5–24.9 kg/m²), overweight (25.0–29.9 kg/m²), or obese (>30.0 kg/m²) [10].
Participants were considered to have hypertension if they had a diagnosis of hypertension and were using medications or if they were newly diagnosed with hypertension, determined as a systolic blood pressure greater than or equal to 140 mm Hg, a diastolic blood pressure greater than or equal to 90 mm Hg, or both [11]. Participants were considered to have diabetes mellitus (DM) if they had already been diagnosed with it and were taking medicine or had been newly diagnosed (their hemoglobin A1c value was ≥ 6.5%), as defined by the International Diabetes Federation [12].
Laboratory investigations
For each participant, 5 mL of blood was taken for the analysis of hemoglobin, HbA1c, and serum creatinine. Ethylenediamine tetraacetic acid (EDTA) tubes were used for hemoglobin and HbA1c analysis, while plain tubes were used for serum analysis (after clotting and centrifugations). An automated hematology analyzer (Sysmex KX-21, Kobe, Japan) was used to measure hemoglobin, following the manufacturer’s instructions. Hemoglobin A1c (whole blood) and serum creatinine (after centrifugation) levels were measured using a Mindray BS-200 Chemistry Analyzer, which is a fully automated analyzer (Mindray Bio-Medical Electronics Co., Ltd., Shenzhen, China). Protein in the urine was assessed using a urinalysis dipstick method (Urine Strip Mission – Protein [Proteinuria] Testing The Mission® Urinalysis Reagent Strips; ACON Laboratories, Inc., San Diego, USA).
The following CKD-EPI equation was used to determine the estimated glomerular filtration rate (eGFR): eGFR = 142 × min (sCr/κ, 1)α × max (sCr/κ, 1) − 1.200 × 0.993Age × 1.012 [if female], where sCr is the serum creatine level, κ is 0.9 for males and 0.7 for females, α is − 0.241 for males and − 0.302 for females, min indicates the minimum value of sCr/κ or 1, and max indicates the maximum value of sCr/κ or 1 [13]. Adults were considered to have CKD if the eGFR was below 60 ml/min/1.73 m2 and/or had proteinuria (positive dipstick at least + 1).
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