Cost-effectiveness of nucleic acid amplification testing to guide treatment for vaginitis: a decision-modeling analysis

Highlights

• Vaginitis can be effectively treated by therapies that specifically target the causative organisms.

• Methods to identify the causative organism differ in diagnostic accuracy and cost.

• This study evaluated the cost and health outcomes for patients with vaginitis under different test-and-treat scenarios.

• Nucleic acid amplification–based test-and-treat scenarios were found to cost-effectively increase the number of patients who achieve resolution of vaginitis symptoms compared with test-and-treat scenarios based on nucleic acid probes or clinical and microscopic examination.

Abstract

We evaluated the cost-effectiveness of test-and-treat scenarios for vaginitis, scenarios based on clinical and microscopic examination (CME), nucleic acid amplification testing (NAAT), or nonamplified nucleic acid probe (probe) testing. The symptom resolution outcome and the payer cost of diagnosis and treatment were estimated in decision analytical models in a hypothetical patient population. Compared with probe testing, NAAT resulted in symptom resolution in more patients (615 versus 475 per 1000 tested) at a cost of $210 per incremental symptom resolution, a cost lower than the willingness to pay for symptom resolution ($871) implied by payer coverage for probe testing. Following a negative CME, the NAAT scenario resulted in symptom resolution in more patients (650 per 1000 patients tested) than did either CME (525) or the CME probe testing–based scenario (602) at incremental cost-effectiveness ratios lower than the willingness to pay implied by coverage for CME. Therefore, NAAT is likely to cost-effectively improve health outcomes for patients with vaginitis.

Introduction

Vaginitis is one of the most common gynecologic conditions, accounting for over 10 million physician office visits each year in the United States (Kent, 1991; Paladine and Desai, 2018; Sobel et al., n.d.). The 3 most common infectious causes of vaginitis in the primary care setting are bacterial vaginosis (BV; 22% to 50% of cases), vulvovaginal candidiasis (VVC; 17% to 39% of cases), and Trichomonas vaginalis (TV; 4% to 35% of cases), with about 30% of the cases having an indeterminate cause (Anderson et al., 2004; Hainer and Gibson, 2011). If left untreated, vaginitis can increase a woman's risk of other health problems. For example, BV has been associated with pelvic inflammatory disease and increased susceptibility to HIV infection (Onderdonk et al., 2016).

Drugs that target the causative microorganism are highly effective, resolving symptoms in more than 80% of the patients treated (Carr et al., 2005). Therefore, accurate identification of the causative microorganisms is important to guide the prescription of targeted antimicrobial therapy. Accurate diagnosis and treatment with the appropriately targeted therapy not only relieve symptoms but also provide other potential health benefits such as reducing the risk of acquiring sexually transmitted diseases (Centers for Disease Control and Prevention, n.d.). Accurate diagnosis and treatment could also reduce the costs associated with unresolved symptoms and complications. In North America, the annual economic burden of treating symptomatic BV is estimated at US$1.3 billion, a cost that would be even higher if the cost of BV-associated complications was included (Peebles et al., 2019).

Options for assessing the cause of vaginitis include clinical and microscopic examination (CME), nucleic acid amplification testing (NAAT), and nonamplified nucleic acid probe (probe) testing (Andrea and Chapin, 2011; Cartwright et al., 2013; Gaydos et al., 2017; Richter et al., 2019; Schwebke et al., 2018; Thompson et al., 2020). CME relies on the evaluation of clinical symptoms, measurement of vaginal pH, amine (whiff) test, and KOH or wet mount microscopy. NAAT and probe testing can simultaneously identify the 3 types of microbial pathogens (bacteria, Candida spp., and Trichomonas vaginalis)—NAAT uses real-time polymerase chain reaction (PCR) for amplification of pathogen DNA targets, while the DNA probe–based test hybridizes nucleic acid probes to unamplified pathogen DNA in vaginal fluid specimens. CME has been traditionally used in the clinic, but the sensitivity for microbial pathogens is low, ranging from 58% for VVC to 77% for BV (Schwebke et al., 2018). CME also requires expertise in microscopy and an on-site microscope, making CME impractical in many primary care settings. Probe testing has higher sensitivity for BV (~90%), but the sensitivity is 58% for VVC and 46% for TV (Cartwright et al., 2013). In contrast, NAAT has 97% sensitivity for all 3 types of microbial pathogens. Overall, these 3 diagnostic methods have relatively high specificity, except that probe testing has only modest specificity for BV (Cartwright et al., 2013).

Given that CME, NAAT, and probe testing differ in both diagnostic accuracy and cost, a better understanding of the cost-effectiveness of test-and-treat scenarios based on these 3 diagnostic methods could help inform healthcare decisions. Ackerman et al. recently analyzed commercial healthcare insurance claims during the 6-month period after patients sought treatment for vaginitis (Ackerman et al., 2019). They found that all-cause healthcare resource utilization and all-cause direct costs were lower for the group that used NAAT than for the group that used probe testing. However, since this was a retrospective analysis and patients were not randomized between NAAT and probe testing, differences in patient or physician characteristics may have influenced the results (Sherman et al., 2016). Furthermore, the analysis of health insurance data may not have always captured CME that was done in addition to a NAAT or probe test because healthcare providers may not take the time to bill for the small fee allowed for the performance of a CME. Therefore, we have used a decision-modeling analysis to evaluate the cost-effectiveness of a test-and-treat scenario based on NAAT compared with a scenario based on probe testing. We also evaluated the cost-effectiveness of using either NAAT or probe testing as a follow-up test after a negative or indeterminate CME diagnosis compared with using CME alone. This study was conducted from a payer perspective in the United States.