Controversyillustrates the problems that researchers face in arriving at “normal” clinicalvalues.
Agreement on what are normal values in medicine often is aprerequisite to the development of clinical guidelines. But what happens ifguidelines are based on arguable definitions of normal?
The result could be themisdiagnosis of patients, as contended recently by Richard J. Glassock, MD, emeritusprofessor at the David Geffen School of Medicine, Universityof California, LosAngeles, and U.K.nephrologist Christopher Winearls, MD. Drs. Glassock and Winearls challengedguidelines for diagnosing CKD and assert that many individuals are beingwrongly diagnosed as having renal disease.
First, some background. Last October, the U.S. Renal DataSystem (USRDS) announced that a 30% increase in CKD over the past decade hadprompted this division of the National Institute of Diabetes and Digestive andKidney Diseases (NIDDK) to issue its first-ever separate report documenting themagnitude of this condition. According to the USRDS, CKD affects an estimated27 million Americans. The accuracy of this estimate, however, depends on whatglomerular filtration rate (GFR) is considered normal.
Dr. Glassock observed that the CKD definition used by theNational Kidney Foundation (NKF) Kidney Disease Outcomes Quality Initiative(KDOQI) guidelines “encompasses a significant number of normal people anderroneously—at least in my opinion—defines them as having disease.
When patientsare diagnosed with CKD but don’t have it, the potential harm ranges fromcausing them anxiety and worry to undergoing expensive testing to possibly evenlosing their health insurance.”
The controversy stems from the fact that serum creatininemeasurements are done in nearly all inpatients and a high percentage ofoutpatients, even those simply making routine visits for preventive primarycare. “Whenever a serum creatinine test is done, an estimated glomerularfiltration rate, or eGFR, is also calculated according to the standard MDRD[Modification of Diet in Renal Disease study] equation,” Dr. Glassock explains.