SLR - April 2016 - Nicholas A. Ciotola
Reference: Mikailov A, Cohen J, Joyce C, Mostaghimi A. Cost-effectiveness of Confirmatory Testing Before Treatment of Onychomycosis. JAMA Dermatol. 2016 Mar 1;152(3):276-81Scientific Literature Review
Reviewed By: Nicholas A. Ciotola, DPM
Residency Program: Lenox Hill Hospital
Podiatric Relevance: In 1999, the American Academy of Dermatology offered the recommendation that confirmatory testing is favorable and cost-effective in the diagnosis and treatment of onychomycosis. Since then, the cost of treating onychomycosis has decreased. At the same time, a benign side-effect profile has emerged for terbinafine. The study authors undertook to estimate the costs of treating onychomycosis empirically versus obtaining laboratory confirmation of onychomycosis prior to treatment.
Methods: A decision analysis was performed over three different treatment algorithms: (1) immediate treatment of patients without testing, (2) immediate KOH testing in clinic with immediate treatment for KOH-positive patients and PAS testing for those who were KOH-negative before initiating treatment, and (3) PAS testing before treatment. The authors conducted a literature review of prospective studies to determine sensitivity and specificity of laboratory testing. The authors identified costs of terbinafine and efinaconazole by contacting pharmacies. They further used the Centers for Medicare and Medicaid Services to identify costs of diagnostic laboratory testing as well as liver function tests. With this information, they were able to perform separate decision tree analyses to estimate the costs assuming prevalances of onychomycosis of 30 percent, 60 percent, and 90 percent in patient populations seeking treatment for onychodystrophy.
Results: The cost of treating onychomycosis with a 12-week course of terbinafine while monitoring liver enzymes was $53. The cost of treating one toenail with efinaconazole was $2307. The cost of confirmatory testing was $6 for KOH and $148 for PAS. The net costs associated with the KOH screening algorithm increased with terbinafine for higher disease prevalence but decreased for efinaconazole with higher disease prevalence. The net costs associated with the PAS screening algorithm increased as prevalence increased from 30% to 90% for both oral and topical antifungals. This is because, in each model, a higher percentage of true positives and true negatives would be identified as prevalence increases. In other words, at higher rates of prevalence, fewer patients received inappropriate treatment. The authors found that confirmatory testing increased the cost of a course of terbinafine but was associated with a cost savings in efinaconazole. Assuming onychomycosis prevalence of 75 percent and an incidence of clinically apparent liver injury due to terbinafine of 1 case per 50,000 to 120,000, the cost of testing to avoid one such liver injury is between $18.2 and $43.7 million using KOH screening and between $37.6 and $90.2 million using PAS screening.
Conclusions: While the risks of complications associated with terbinafine are worthy of consideration, these results suggest a substantial economic burden associated with diagnostic testing. In contrast, confirmatory testing has been demonstrated to generate a cost savings for efinaconazole, which carries a multiplicative benefit per involved nail. The authors conclude that the changing landscape of pharmaceutical costs necessitates a shift in diagnostic practices. For the podiatrist, empirical treatment onychomycosis with terbinafine should be regarded as a safe and economical option. The podiatrist considering efinaconazole as a therapy would be advised to obtain laboratory confirmation to avoid inappropriate use of this expensive agent.