800 infection control & hospital epidemiology july 2018, vol. 39, no. 7


Correlation of Antibiotic Utilization With Mortality and Days of Significant Illness


Hospital 30-day mortality rates ranged from 0 to 9.5%, with a median of 2.1% overall. Days of significant illness ranged from 0 to 115 days per 1,000 neutropenic days (Table 1). The Spearman correlation coefficients between specific antibiotic groups and mortality rates and DSIs are shown in Table 2. Mortality was not correlatedwith any antibiotic group. Days of significant illness were moderately positively correlated with gram-positive antibiotic use and moderately negatively corre- lated with antipseudomonal antibiotic use; no correlation with carbapenems was identified.


Hospital Rates of Antibiotic Utilization


Overall, 90.1% of patients received at least 1 day of a broad- spectrum antipseudomonal or gram-positive antibiotic; the proportion by hospital ranged from 64.7% to 100% for anti- pseudomonal antibiotic receipt and from 50% to 100% for gram-positive antibiotic receipt. Composite unadjusted anti- pseudomonal DOTs per 1,000 neutropenic days ranged from 424 to 1012 (median, 731); for carbapenems specifically, DOTs ranged from 415 to 987 (median, 719); and for gram-positive


Time to Engraftment (median, d)


27 7


26 12 15 25 17 19 8


13 22 4 2


20 1 5 3


11 18 9


24 14 10


Full cohort 770 NOTE. DSI, days of significant illness.


21.7 23.7 23.7 19.3 21.2 16.8 20.7 18.2 15.8 22.7 26.7 19.7 19.2 22.7 18.3 13.8 24.7 15.8 16.8 24.7 20.7 24.7 23.7 15.8 19.2 21.7 17.8 19.7


antibiotics, DOTs varied from 148 to 824 (median, 399). In the negative binomial models, adjusted hospital DOTs varied minimally from unadjusted estimates, and the scope of the variability across hospitals was similar (Figures 2 and 3). As demonstrated in Figure 2a, the choice of antipseudomonal agents varied across hospitals. In contrast, gram-positive antibiotic utilization was driven primarily by vancomycin prescribing (Figure 3). The sensitivity analysis restricting the evaluation to only the later years did not meaningfully change the rates of utilization between hospitals, nor did the exclusion of DSIs from the adjusted models.


Drivers of Variation in Antibiotic Utilization


In the base ME models that included only hospital-level ran- dom effects, the estimated variance is statistically significantly different from zero, suggesting significant variation in anti- biotic utilization across hospitals. As indicated by a higher point estimate of variance, this variability is more pronounced for gram-positive antibiotics and carbapenems compared to antipseudomonal antibiotics (Table 3). In each of the 3 mod- els, the point estimate of variance decreased with the addition of patient- and hospital-level factors. However, despite the


table 1. Descriptive Characteristics of 27 Hospitals Included in the Analysis Hospital No. No. of Patients


Age


21 16 23 6


13 14 15 16 16 17 17 18 19 19 21 21 22 22 23 24 28 28 34 39 40 40 40 48 50 61 65


(median, y) 12.4


10.4 8.5


13.2 11.5 10.7 8.8


10.1 10.4 10.8 9.6 7.3


12.0 9.6 9.2 8.6 9.1 6.8


10.7 6.6 9.7 8.5 7.7 8.7


11.4 10.0 8.6 9.6


44 31 29 47 48 43 43 50 33 36 37 44 38 29 48 56 29 41 33 31 34 50 44 43 37 43 41


Sex


(female, %) 41


Race


(nonwhite, %) 18


35 0


18 0


38 30


9.2


36 14 30 11 13 21 29


8.7


22 64 41 25 56 18 18 10 15 0


36 22


DSI/1,000


Neutropenic Days 89


97 0


20 83 74 27 0 6 0


14 72 0


115 94 22 51 55 39 10 11 63 24 55 6


48 33 39


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