A multicenter evaluation of variables affecting the predictability of creatinine clearance.

Data from 722 urine collections (627 patients) from 14 medical facilities were used to compare measured creatinine clearance values with clearance estimates calculated using three "urine-free' mathematical formulas. The influence of two patient weight variables (actual weight, lean body weight) and the level of renal function on clearance prediction was assessed. In addition, site parameters (region, facility), time parameters (month, day, day of the week), and patient parameters (age, sex, height, weight, diagnoses) were evaluated for their statistical influence on the relationship between measured clearance and estimates calculated with one of the methods. Strong, statistically significant correlations were observed between clearance values estimated with each prediction method and measured clearances. Although statistical differences were noticed between mean values predicted with each method, these differences were clinically insignificant. Use of lean body weight for calculation of creatinine excretion produced clearance estimates that were significantly lower than those obtained with actual weight and substantially closer to measured clearance values. Among patient variables, age and two specific diagnoses (congestive heart failure and pregnancy), were statistically associated with variability in the relationship between measured and predicted clearance. Interregional and interfacility differences in the measured-predicted clearance relationship, variability associated with the day of the week of collection, and tendency of the urine-free formulas to over-predict clearance support potential inaccuracy of measured clearance determination. The results suggest that inaccuracies in clearance determination, rather than inadequacies of urine-free prediction methods, account for the majority of the observed variability in the relationship.

Simple method to predict digoxin serum concentration.

The predictability of a method of determining serum digoxin concentration was assessed in a retrospective study of 35 hospitalized patients taking digoxin orally for maintenance therapy. Simple pharmacokinetic expressions were used to estimate digoxin concentration. Clinically, the mean measured digoxin concentration (1.35 ng/ml) was in close agreement with the mean predicted value (1.36 ng/ml). There was also a strong statistical correlation between measured and predicted values (r = .82). The predictability of serum digoxin concentration was statistically equivalent in men and women. Our results indicate that a reasonably accurate prediction of digoxin concentration is possible using simple mathematical formulas that require only routine clinical data.

Community, hospital and clinical pharmacists and drug information centers as physician drug information sources.

The use of drug information centers and clinical, hospital and community pharmacists by university and community practice physicians in North Carolina was examined. Questionnaires were sent to 674 nonfederal physicians with a response rate of 203 (35.5%). Approximately half of the sample were staff members of a university hospital. The questionnaire covered eight types of drug information. Significant results were reported at the p = 0.05 level. Physicians sought specific drug information approximately one to four times a month. University hospital-affiliated physicians rated clinical and hospital pharmacists significantly higher than community pharmacists for six subject areas, and they also ranked clinical pharmacists over hospital pharmacists on four subject areas and considered them more reliable than other pharmacy drug information sources. Physicians associated with community hospitals ranked hospital pharmacists over community pharmacists as sources of information for four areas and rated them more reliable than other pharmacy drug information sources; this group preferred to use community pharmacists for information on product availability. It appears that clinical pharmacists are used by university-associated physicians as drug information sources. Use in community hospitals of the hospital pharmacist as a drug information source is better than the literature might suggest.