Comparison of Three A Priori Methods and One Empirical Method in Predicting Lithium Dosage Requirements

Results

The records of 47 patients were accepted for the study. The demographic characteristics of the patients are summarized in Table 1.

Mean error results for predicted dosage and serum lithium C_ss are summarized in Table 2. The frequency distributions of dosage prediction errors for the four methods are shown in Figure 1.

(Enlarge Image)

Frequency distribution of dosage prediction errors for the Jermain method (white), the Pepin method (black), the Zetin method (diagonal stripes), and the empirical method (vertical stripes).

The Jermain and empirical methods had a significant tendency to overpredict concentration and underpredict dosage. The Zetin method was the only method that significantly overpredicted dosage. The Pepin method significantly underpredicted dosage but had no corresponding tendency to overpredict concentration; instead, the Pepin method tended to underpredict concentration, although not significantly.

One-way ANOVA for absolute mean dosage prediction error showed overall significant differences among methods (p = 0.046). However, pairwise post hoc comparisons did not reveal significant differences. ANOVA for absolute mean prediction error for serum concentration showed significant differences among methods (p = 0.0001). In post hoc comparisons, the Jermain and Pepin methods were significantly more precise than the empirical method (p = 0.0005 and p = 0.002, respectively).

Analysis of the clinical significance of dosage prediction errors showed that the Jermain and Zetin methods predicted significantly more dosages within 20% of actual than the empirical method (X² = 5.824, p = 0.016 and X²= 6.823, p = 0.009, respectively). No other differences between methods were statistically significant.

Am J Health Syst Pharm. 2000;57(18) © 2000 American Society of Health-System Pharmacists

Presented at the ASHP Midyear Clinical Meeting, Las Vegas, NV, December 6, 1995. Copyright © 2000, American Society of Health-System Pharmacists, Inc.

Cite this: Comparison of Three A Priori Methods and One Empirical Method in Predicting Lithium Dosage Requirements - Medscape - Sep 15, 2000.