Underestimating chronic kidney disease by urine dipstick without serum creatinine as a screening tool in the general Japanese population

It is not known if urine dipstick alone can identify chronic kidney disease (CKD) in the general Japanese population. We designed a cross-sectional study using data obtained in 2008 from a nationwide community-based health examination program for adults aged 40-74. The data consisted of blood tests, urine tests and questionnaire related to metabolic disorders. Those who had both serum creatinine measured and urine dipstick tested were analyzed. Data were obtained from 538,846 people with a mean age of 62.8 years, consisting of 41.6 % males. Our study showed that 14.4 % had an eGFR below 60 mL/min/1.73 m(2), 5.2 % had proteinuria and 18.1 % had CKD. Within the population with CKD, non-proteinuric CKD accounted for 71.4 %. The proportion of non-proteinuric CKD was highest in stage G3a (91.8 %) followed by G3b (77.0 %) disease, and was greater in the more elderly and in females. The proportion of non-proteinuric CKD was 47.9 % in diabetes mellitus, 69.3 % in dyslipidemia, 66.8 % in hypertension and 57.1 % in metabolic syndrome. Furthermore, non-proteinuric CKD accounted for 78.1 % of the population without these lifestyle diseases, suggesting that even in the population without apparent risk, CKD is still prevalent and can be missed when urine dipstick is the only screening method used. This study showed that a considerable population of CKD might be overlooked when only dipstick proteinuria is assessed for CKD screening. Hence, we strongly recommend that both urinalysis and serum creatinine measurement should be a part of the nationwide CKD screening system.