Normality data of eGFR and validity of commonly used screening tests for CKD in an area with endemic CKD of unknown etiology; need for age and sex based precise cutoff values

BACKGROUND: Chronic Kidney Disease in certain part of Sri Lanka and increasing burden of CKD in some other countries is a global public health problem. While the underlying causes of majority of cases are unknown, effective control and prevention strategies are yet to be taken. Though the disease has been identify more than decade ago, baseline data on renal function are not available. This study reports the age and sex disaggregated data of renal functions among screening participants of the Anuradhapura, the district with the highest disease burden in Sri Lanka. METHODS: The screening prorgramme was done as a part of CKD control programme of Anuradhapura. All screening centers were visited and information and urine sample collection tubes were distributed before the screening date. A serum and urine sample was taken from all participants. In a subsample, urine sulfosalicylic acid test (SSA Test), urine dipstick test, urine albumin to creatinine ratio (UACR) and urine protein to creatinine ratio (UPCR) was done. RESULTS: The study sample included 7768 apparently healthy people aging 18 to 93 years and females (n = 5522) accounted for 71.1% of the sample. Mean age of the participants was 45.9 (SD 14.1) years. Mean eGFR in this population was 90.8 mL/min/1.73m(2)(SD 24.6) with a significantly lower eGFR (88.1 mL/min/1.73m(2)) among males compared to female (92.8 mL/min/1.73m(2)). Mean eGFR was 115 mL/min/1.73m(2) (SE .5) among participants aging less than 30 and this value drastically reduced to 59.1 mL/min/1.73m(2) (SE 1.2) among people aging more than 70 years. Proportion of people having reduction of eGFR compatible with mild, moderate, severe and kidney failure categories was 33.9(32.7–34.8), 8.4(7.8–9.0), 1.5(1.2–1.7) and 0.7(0.5–0.9). The age and sex adjusted prevalence of eGFR less than 60 mL/min/1.73 m2 in a single sample in this population was 10.6%. Bayesian Latent Class model analysis shows that UPCR> 150 has the highest sensitivity to detect those who are with eGFR less than 60 mL/min/1.73 m2. UACR, the usual recommended test as a screening test was having a sensitivity of 35.3% in this population. CONCLUSION: UPCR and UACR should be use as a screening tests in areas with high proportion of CKDu patients. More research are required to investigate the use of age and sex specific cut off values to diagnose CKD.