Norra MacReady

November 05, 2009

November 5, 2009 (San Diego, California) — Women are more likely than men to have undiagnosed chronic kidney disease (CKD), except in its later stages, investigators announced here at Renal Week 2009, the annual meeting of the American Society of Nephrology.

These findings illustrate the importance of using automatic estimated glomerular filtration rate (eGFR), rather than serum creatinine (SCr), to diagnose CKD, said Maya K. Rao, MD, an instructor of clinical medicine in the Division of Nephrology at the Columbia University College of Physicians and Surgeons in New York City, who presented the findings in a poster session. With automatic eGFR reporting, the difference in undiagnosed CKD between the sexes was statistically insignificant.

Dr. Rao and her colleagues conducted a retrospective chart review of 883 people attending 18 primary care clinics in rural Oregon. The inclusion criteria were a SCr level higher than 1.5 mg/dL for men and a SCr level higher than 1.3 mg/dL for women. Normal SCr levels range from 0.8 mg/dL to 1.4 mg/dL. eGFR was then calculated using the Modification of Diet in Renal Disease formula, which uses SCr levels along with age, race, and sex to arrive at the patient's eGFR. This analysis included only patients with an eGFR less than 60 mL/minute/1.73 m2, which suggests stage 3 kidney damage and moderately impaired glomerular function.

CKD was undiagnosed in 93.3% of the women with an eGFR of 45 to 59 mL/minute/1.73 m2 compared with 59.1% of the men, for an odds ratio of 14.6. When eGFR was 30 to 44 mL/minute/1.73 m2, CKD was undiagnosed in 63.3% of the women and 39.9% of the men, respectively. At an eGFR of less than 30 mL/minute/1.73 m2, the diagnosis was missed in 30.5% of the women and 22.2% of the men.

In practices that used automatic laboratory eGFR reporting, CKD was undiagnosed in 51.3% of the women and 47.1% of the men. When diagnosis was based only on SCr levels, CKD was missed in 63.7% of the women and 43% of the men, for a women-to-man odds ratio of 2.31.

The sex disparities occurred regardless of the clinician's medical training or level of education, the investigators wrote. "Even among patients with diabetes, 30% had no diagnosis of CKD," Dr. Rao told Medscape Nephrology.

Creatinine is a breakdown product of the muscle component creatine, said Dr. Rao. It is excreted through the kidneys, so SCr levels climb as renal function declines. Women normally have lower SCr levels than men because of their smaller muscle mass.

The absence of sex disparity when automatic eGFR reporting was used "makes me think [the failure to diagnose CKD in women] is due to the fact that doctors don't recognize that women normally have lower SCr levels," she explained. "Most laboratories evaluate kidney function using serum creatinine, but eGFR is the true measure of kidney function."

These data "make perfect sense," said independent observer Elizabeth Hedgeman, MS, MPH, an epidemiologist at the Kidney Epidemiology and Cost Center at the University of Michigan, Ann Arbor. "The lower SCr in women is not surprising, but since it won't look abnormally high to the doctor, they won't diagnose it as CKD."

Patients in rural settings usually do not have access to specialists, so it is up to the primary care clinician to diagnose and treat CKD, Dr. Rao warned. "Automatic eGFR reporting is a simple thing that could be done that could help more people recognize CKD."

Dr. Rao and Ms. Hedgeman have disclosed no relevant financial relationships.

Renal Week 2009: American Society of Nephrology 2009 Annual Meeting: Poster Abstract SA-PO2316. Presented October 31, 2009.

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