Natural history of elevated creatinine levels.

OBJECTIVE To investigate what happens to the serum creatinine (SC) levels of people with initial mild elevations in SC; whether a stable, non-progressive elevation in SC level is the most common scenario; how common a progressive increase in SC is among primary care patients; and how often primary care patients with substantial elevations in SC (>300 micromol/L) progress to end-stage renal disease. DESIGN Retrospective analysis of laboratory data and chart review. SETTING Queen's University Family Medicine Centre in Kingston, Ont. PARTICIPANTS All patients who had SC levels measured at a nearby hospital laboratory between January 1994 and December 1998. MAIN OUTCOME MEASURES Recently recorded height and weight measurements, latest SC measurements (if available), whether patients had been referred to nephrologists, comorbidity, medications being taken, whether patients were currently undergoing dialysis or had received a renal transplant, and whether patients had died. RESULTS In the 1434 charts of eligible patients, 64 (4.5%) had elevated initial SC levels (>130 micromol/L) recorded, and 57 of these contained follow-up SC levels also. Among these 57 patients, 32 (56%) saw their SC levels return to normal, including 50% of those whose initial levels had been >300 micromol/L. Only 7 patients (12%) with elevated SC levels progressed to higher levels during the follow-up period. Average age in the study group was 63 years; those with initial elevated SC levels were older than the average (70 years). CONCLUSION More than half of those with initially elevated SC levels (>130 micromol/L) saw their levels return to normal, including patients whose initial levels had been >300 micromol/L. It seems that a single elevated SC measurement does not predict ongoing decline in renal function.