Conclusions: The CG and MDRD formulas had some limitations for proper GFR estimation and K/DOQI-CKD classification by GFR levels alone.

SummaryThe GFR has a paramount diagnostic and staging role in the Kidney Disease Outcome Quality Initiative Clinical Practice Guidelines for Chronic Kidney Disease (K/DOQI-CKD). The most widely used serum creatininebased formulas in adults for estimated GFR (eGFR) are the Cockcroft-Gault (CG) and Modification of Diet in Renal Disease Study (MDRD). Recently, a new Chronic Kidney Disease Epidemiology Collaboration equation has been developed. Review of the literature revealed that CG and MDRD formulas correctly assigned overall only 64% and 62%, respectively, of the subjects to their actual K/DOQI-CKD classification's GFR groups as determined by measured GFR (mGFR). This suggests that approximately 10 million (38%) subjects may have been misclassified on the basis of estimated CKD prevalence of 26.3 million adults in the United States. The purpose of this review is to help the clinician understand the limitations of using eGFR in daily practice. We also elaborate upon issues such as the differences among markers of mGFR, the validity of adjusting GFR for body surface area in certain populations, the limited data on boundaries for normal mGFR according to age, gender, and race, the need for calibration of a wide spectrum of serum creatinine measurements, the lack of actual eGFR value above 60 ml/min per 1.73 m 2 and reference for normal mGFR in the clinical laboratories' reports, and the performance evaluation of the eGFR formulas. Several pitfalls have to be overcome before we can reliably determine health and disease in daily nephrology practice to preserve the first rule of practicing medicine: primum non nocere.Clin J Am Soc Nephrol 6: 937-950, 2011.

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Objectives Sexual and erectile dysfunction (ED) have been reported to occur frequently in male patients with end-stage renal disease maintained on dialysis. Numerous etiologies for this ED have been suggested. Although a variety of therapies for the ED of the dialysis patient have been suggested, most clinicians indicate that patients report a poor response to therapy. Recently, sildenafil has been reported to be beneficial in treating patients with ED of both organic and psychogenic causes. The present study was designed to document the incidence of ED in male patients maintained on chronic peritoneal dialysis (CPD) and to determine the efficacy of prescribing sildenafil therapy to treat their ED. Methods All male patients in our CPD unit were notified by letter of the availability of sildenafil as a treatment modality for ED. A sexuality/erectile dysfunction assessment was conducted in all male patients by their primary nephrologist. Patients who reported ED and who had no medical contraindication to sildenafil were offered this therapy. Those patients who were interested in this treatment were interviewed by a social worker, and patients were asked to complete the International Index of Erectile Function questionnaire. Sildenafil was prescribed at a starting dose of 25 mg and increased to a maximum of 100 mg during a 12-week study trial. Patients were re-evaluated 6 and 12 weeks after the start of therapy. Results There were 68 male patients maintained on CPD at the time of the study. Mean age of all patients was 60.8 ± 15.3 years and mean duration on PD was 32.6 ± 25.6 months. Thirty-three patients had diabetes, 66 hypertension, 35 peripheral vascular disease, and 32 coronary artery disease. Thirty-two of 68 male patients in the CPD unit were assessed to have ED. Only 17 of the 32 patients expressed interest in pursuing sildenafil therapy. Two of these patients were excluded because they were receiving nitrate therapy. Of the 15 patients who agreed to take sildenafil, only 6 completed the 12-week study. Two of these patients responded to sildenafil. Conclusion Erectile dysfunction is common in male patients maintained on CPD. Only about half of patients with ED in the present study were willing to consider sildenafil therapy to treat the ED and, of those who agreed to treatment, only a minority completed the 12-week trial; 2 of these 6 patients reported a satisfactory response.