Pharmacoeconomics of antifungal therapy: current considerations:

Clinical validity of bis(methylthio)gliotoxin for the diagnosis of invasive aspergillosis

Early and accurate diagnosis of invasive aspergillosis (IA) is one of the most critical steps needed to efficiently treat the infection and reduce the high mortality rates that can occur. We have previously found that the Aspergillus spp. secondary metabolite, bis(methylthio)gliotoxin (bmGT), can be detected in the serum from patients with possible/probable IA. Thus, it could be used as a diagnosis marker of the infection. However, there is no data available concerning the sensitivity, specificity and performance of bmGT to detect the infection. Here, we have performed a prospective study comparing bmGT detection with galactomannan (GM), the most frequently used and adopted approach for IA diagnosis, in 357 sera from 90 episodes of patients at risk of IA. Our results, involving 79 patients that finally met inclusion criteria, suggest that bmGT presents higher sensitivity and positive predictive value (PPV) than GM and similar specificity and negative predictive value (NPV). Importantly, the combination of GM and bmGT increased the PPV (100 %) and NPV (97.5 %) of the individual biomarkers, demonstrating its potential utility in empirical antifungal treatment guidance and withdrawal. These results indicate that bmGT could be a good biomarker candidate for IA diagnosis and, in combination with GM, could result in highly specific diagnosis of IA and management of patients at risk of infection.

Trends in the utilization of, spending on, and prices for outpatient antifungal agents in US Medicaid programs: 1991-2009

BACKGROUND

The incidence of invasive fungal infections (IFIs) has increased substantially in the recent past. Advances in medical technology, including broad-spectrum antibiotics, may increase the risk for fungal infections. Moreover, immunocompromised patients with cancer, HIV/AIDS, and/or transplants are susceptible to IFIs. Meanwhile, superficial fungal infections (SFIs) are common and can be difficult to cure.

OBJECTIVE

To provide a historical perspective on a dynamic market with expensive medications, this study describes trends in the utilization of, spending on, and average per-prescription spending on outpatient antifungal medications individually, in classes (for IFIs or SFIs), and overall, by the US Medicaid programs from 1991 to 2009.

METHODS

The publicly available Medicaid State Drug Utilization Data, maintained by the Centers for Medicare & Medicaid Services, were used. Annual prescription counts and reimbursement amounts were calculated for each of the antifungals reimbursed by Medicaid. Average per-prescription spending as a proxy for drug price was calculated by dividing reimbursement by the number of prescriptions.

RESULTS

Overall utilization for Medicaid beneficiaries remained steady, with 4.56 million prescriptions in 1991 and 4.51 million in 2009. Expenditures rose from $93.87 million to $143.76 million (in current-year US$) over the same time period. The drop in the utilization of first-generation azoles over the last 5 years of the study period can be explained in part by the movement of dual-eligibles from Medicaid to Medicare Part D and in part to a rise in fungal infections better treated with second-generation azoles or echinocandins. Whereas the average per-prescription price for generic (oral) fluconazole was $8 in 2009, the price per prescription of branded (intravenous) voriconazole was $2178.

CONCLUSIONS

Overall spending by Medicaid on outpatient antifungal medications increased more slowly than did the growth of the Medicaid programs from 1991 to 2009. However, the utilization of antifungal agents for IFIs increased almost 10-fold over this period, far outpacing the rise in the number of Medicaid beneficiaries.