Quantifying the role of factors that limit attainment of K/DOQI urea reduction ratio dialytic goal.

Background: For many ESRD patients who are prescribed a certain level of hemodialysis (HD), delivered dose often does not achieve prescription. While various causes have been well-documented in the literature, there are no available data that may be used in predicting the likelihood of achieving a particular urea reduction ratios (URR) goal based on the number of these factors present. This study evaluated URRs of all patients in an outpatient HD unit for a 6-month period to identify factors significant in attaining goal in order to predict likelihood of goal attainment based on number of factors present.

Methods: The inclusion criterion in this study was any HD patient during the study period with > or = 3 monthly URR measurements. Of 203 patients, 169 qualified for 900 treatments. A database was created for each patient that included demographics, factors affecting K(urea), time and access. After grouping percentages of patients with URR > or = 70%, 65 - < 70%, and < 65%, we studied a subset of 107 patients (568 treatments) that had at least 1 URR < 70% to identify factors associated with a URR of > or = 65% vs. < 65%. To determine factors predictive of URR > or = 65%, a sum percentage across all treatments was created for each patient. Mean percentages were compared between groups created by constant characteristics (e.g. gender, DM). Variables, e.g. catheters, were summarized as a percentage for each patient, and these percentages were correlated with rate of URR > or = 65%. Time was assigned a value of 0 (prescribed), positive (longer), negative (shorter), summarized as per-patient mean. After these factors were identified, each treatment was reviewed to determine the percentage of treatments > or = 65% with the number of statistically significant factors present.

Results: The average, across all patients, of percentage of treatments meeting URR > or = 65% was 87.95% while a mean of 66.65% met URR > or = 70%. Factors associated with percentage of treatments per patient not meeting K/DOQI goal included catheter use (Spearman's correlation = -0.31, p = 0.001), blood flow < 90% of prescription (Spearman's correlation = -0.17, p = 0.041), younger age (> or = 61 years vs. < 61 years, p = 0.001: patients > or = 61 years had a higher percentage of URR > or = 65%), inadequate access for prescribed blood flow (Spearman's correlation = -0.32, p = 0.001), actual time vs. prescribed time (Spearman's correlation = 0.25, p = 0.009), and HD w/o heparin (Spearman's correlation = -0.21, p = 0.031). In 178 treatments, all having "good" values (no catheter, blood flow > or = 90% prescribed, age < or = 61 years, etc.), the percentage of treatments meeting URR of < or = 65 was 96.1%. With 1 bad value factor: 83.8% of 216 treatments met goal, 2 bad value factors: 71.7% of 106 met goal, 3 bad value factors: 60.5% of 43 met goal. With 4 or 5 bad value factors: only 36.1% of 25 treatments met goal.

Conclusions: Significant factors in meeting adequacy defined by K/DOQI in rank order (excluding age) include inadequate access for prescribed blood flow, catheter use, time, lack of heparin and inability to achieve blood flow > or = 90% prescribed. A direct correlation exists between number of these factors present and K/DOQI goal attainment in a given treatment.