PS2-21: The Return on Investment of a Laboratory Program to Decrease Adverse Events of ACE Inhibitors and ARBs

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Introduction: The efficiency of patient safety interventions is not well studied, including laboratory monitoring for drug therapy. Although 30% of patients receiving inhibitors of rennin-angiotensin system (RAS i.e. ACEI and ARB medications) are not monitored according to guidelines, knowledge of the efficiency of decreasing adverse drug events through monitoring programs above usual care is lacking. Methods: We focused on laboratory monitoring of new users of RAS inhibitors to help prevent adverse events of hyperkalemia and acute renal failure. We used a probabilistic decision model to synthesize multiple data sources to inform how increasing monitoring above usual practice changes cost and outcomes from the payer perspective. We accounted for differential timing of costs and benefits and discounted at a 5% rate. Costs included the monitoring program, offsets from reduced care (e.g., hospitalization) and litigation costs. Data from a large integrated health plan were used to estimate the community-based probability of adverse events. The potential to reduce adverse events was estimated from chart review. We examined cost-effectiveness at $30K and $100K per QALY in the overall population, patients with diabetes, and patients with chronic kidney disease (CKD). Results: Adverse events were most common in those with CKD; their cumulative incidence rate was 0.041 (95% CI, 0.047 to 0.037) compared to 0.016 (0.017 to 0.014) and 0.010 (0.011 to 0.010) in the diabetes and overall populations, respectively. Intervening on all new users or the subset with diabetes was cost saving <1% of the time. A monitoring program restricted to patients with CKD was cost saving with a probability of 95% in the base case. In CKD patients, if the program was only half as effective, the probability of cost savings was 65%; if the program had a lower uptake rate (49% instead of 82%) the probability of cost-savings was 30%. Intervening on all patients, or the subset with diabetes, was never cost-effective with a probability exceeding 5%. Intervening on patients with CKD was cost-effective at least 65% of the time even under the most pessimistic scenario. Discussion: Our findings illustrate that, for laboratory monitoring to be cost-effective using commonly accepted definitions, the patient population must be at high enough baseline risk of adverse events. Further inquiry into the willingness to pay for patient safety interventions is needed.