Cost-effectiveness of renal bladder ultrasound after a first time urinary tract infection in children 2-24 months
Thomas Gaither, MD, MAS, Rachel Selekman, MD, MAS, Dhruv S. Kazi, MD, MS, Hillary L. Copp, MD, MS.
University of California, San Francisco, San Francisco, CA, USA.
Background
The American Academy of Pediatrics recommends a screening renal bladder ultrasound for children age 2-24 months after their first febrile urinary tract infection (UTI). However, <1% of ultrasounds in this setting diagnose genitourinary anomalies. Although noninvasive, false positive ultrasounds trigger unnecessary invasive testing. We sought to determine whether the use of ultrasounds after a first febrile UTI is cost-effective in this population.
Methods
We developed a decision analytic model that incorporated prevalence of congenital genitourinary anomalies, probabilities of recurrent UTI, and associated costs and quality adjusted life years (QALYs) (Figure 1). We compared obtaining an ultrasound after a first febrile UTI with deferring the ultrasound until after a second UTI. We used a United States health system perspective and a five-year analytic horizon. We discounted future costs and QALYs at 3% per year. We performed sensitivity analyses to evaluate the robustness of the results to changes in the sensitivity and specificity of ultrasound for vesicoureteral reflux, disutility of a UTI and daily antibiotic prophylaxis for a year. Our primary outcome was incremental cost-effectiveness ratio (ICER) in dollars per QALY. The model was developed using TreeAge Software, Inc (Williamstown, MA).
Results
The probability of a recurrent UTI in the ultrasound arm was 0.199 versus 0.210 in the control arm. Thus, 88 patients would need to be screened with ultrasound to prevent one recurrent UTI. This corresponds to $11,208 to prevent one recurrent UTI. Ultrasound increases QALYs by +0.0002 per person screened, corresponding to an ICER of $756,734/QALY gained. Increased sensitivity of ultrasound to detect reflux exponentially decreases the cost to avoid one UTI. If the sensitivity and specificity of ultrasound to detect reflux were 100% and 94%, respectively, the ICER would become $158,983/QALY gained. The ICER falls below $100,000/QALY gained if the annual disutility for recurrent UTI were 0.11 and that for daily prophylaxis were 0. If the prevalence of all other treatable anomalies (posterior urethral valves, UPJ obstruction, ureterocele, obstructing megaureter, non-obstructing megaureter, high-grade non-obstructing hydronephrosis) increased by 0.4%, the resulting ICER would be $63,003/QALY gained. This corresponds to a total prevalence of genitourinary anomalies of 3.4% with the base case prevalence of vesicoureteral reflux.
Conclusions
Screening ultrasound after a first UTI in children 2-24 months is not cost-effective at a willingness to pay threshold of $100,000 per QALY gained, but would be improved with increasing sensitivity of ultrasound to detect reflux. The disutility of one recurrent UTI would have to be similar to having CKD, stage 2 (~0.11 annual disutility) in order for ultrasound to become cost-effective. Varying the prevalence of genitourinary anomalies certainly impacts the benefit of screening
ultrasonography. However, currently reported prevalence in this setting is well below the threshold to make ultrasound cost-effective. Our findings do not support current recommendations to screen children with a ultrasound after a first febrile UTI. 
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