DENVER – When patients with stage 3 chronic kidney disease develop anemia, they have a worse clinical course, according to results of a multicenter study in Spain.
"Anemia is a very complicated cardiovascular risk factor. It appears early in many (chronic kidney disease) patients, especially in the diabetic population," Dr. Alberto M. Castelao said in an interview during a poster session at the annual meeting of the American Society of Nephrology.
He and his associates evaluated data from 431 patients aged 18-78 years who were enrolled in the Study of Non-Anaemic Stage 3 CKD Patients Who Develop Renal Anaemia (NADIR-3), an epidemiologic, prospective, 3-year trial conducted at 27 centers in Spain. At baseline, the patients had a mean estimated glomerular filtration rate of 30-59 mL/min per 1.73m2 without anemia. They were followed every 6 months until they started renal replacement therapy or died.
If anemia occurred, the researchers conducted a diagnostic study to rule out causes not related to chronic kidney disease. In women, anemia was defined as a hemoglobin of less than 11.5 g/dL. In men, anemia was defined as a hemoglobin of less than 13.5 g/dL in those aged younger than 70 years and a level of less than 12.0 g/dL in men aged 70 and older.
Dr. Castelao, a nephrologist who practices in Bellvitge, Spain, reported that the mean age of the 431 patients was 63 years and 70% were male. Nearly one-third (30%) developed anemia – 85% from a renal cause – over the time period. The probability of developing anemia was 10% at 1 year, 20% at 2 years, and 26% at 3 years. The mean time to onset of anemia was 35 months.
Compared to patients without anemia, those who developed anemia had lower baseline estimated glomerular filtration rate (35.9 mL/min per 1.73m2 vs. 40.0 mL/min per 1.73m2, respectively), greater baseline proteinuria (0.94 g/day vs. 0.62 g/day), lower albumin (4.1 g/dL vs. 4.3 g/dL), greater reduction of estimated glomerular filtration rate (6.8 mL/min per 1.73m2 vs. 1.6 mL/min per 1.73m2 at 3 years), earlier progression to stage 4 CKD (18 months vs. 28 months), and greater rate of major cardiovascular events (16.1% vs. 6.9%), hospitalization (33.7% vs. 19.4%), and mortality (10.3% vs. 6.6%). All differences between the two groups were statistically significant.
"If we can stop anemia early, perhaps we can stabilize the renal function," Dr. Castelao said.
The study was sponsored by the Spanish Group for the Study of Diabetic Nephropathy. It received financial support from Amgen. Dr. Castelao said that he had no relevant financial disclosures.