Cost-effectiveness of human T-cell leukemia virus type 1 (HTLV-1) antenatal screening for prevention of mother-to-child transmission

Background: Human T-cell leukemia virus type 1 (HTLV-1) causes adult T-cell leukemia-lymphoma (ATL) and HTLV-1-associated myelopathy-tropical spastic paraparesis (HAM/TSP) with a poor prognosis. This study aimed to evaluate the cost-effectiveness and health impact of HTLV-1 antenatal screening. Methodology/Principal findings: A state-transition model was developed for HTLV-1 antenatal screening and no screening over a lifetime horizon from a healthcare payer perspective. A hypothetical cohort of 30-year-old individuals was targeted. The main outcomes were costs, quality-adjusted life-years (QALYs), life expectancy life-years (LYs), incremental cost-effectiveness ratios (ICERs), HTLV-1 carriers, ATL cases, HAM/TSP cases, ATL-associated deaths, and HAM/TSP-associated deaths. The willingness-to-pay (WTP) threshold was set at US$50,000 per QALY gained. In the base-case analysis, HTLV-1 antenatal screening (US$76.85, 24.94766 QALYs, 24.94813 LYs, ICER; US$40,100 per QALY gained) was cost-effective compared with no screening (US$2.18, 24.94580 QALYs, 24.94807 LYs). Cost-effectiveness was sensitive to the maternal HTLV-1 seropositivity rate, HTLV-1 transmission rate with long-term breastfeeding from HTLV-1 seropositive mothers to children, and the cost of the HTLV-1 antibody test. HTLV-1 antenatal screening was cost-effective when the maternal HTLV-1 seropositivity rate was greater than 0.0022 and the cost of the HTLV-1 antibody test was lower than US$94.8. Probabilistic sensitivity analysis using a second-order Monte-Carlo simulation showed that HTLV-1 antenatal screening was 81.1% cost-effective at a WTP threshold of US$50,000 per QALY gained. For 10,517,942 individuals born between 2011 and 2021, HTLV-1 antenatal screening costs US$785 million, increases19,586 QALYs and 631 LYs, and prevents 125,421 HTLV-1 carriers, 4,405 ATL cases, 3,035 ATL-associated deaths, 67 HAM/TSP cases, and 60 HAM/TSP-associated deaths, compared with no screening over a lifetime. Conclusion/Significance: HTLV-1 antenatal screening is cost-effective and has the potential to reduce ATL and HAM/TSP morbidity and mortality in Japan. The findings strongly support the recommendation for HTLV-1 antenatal screening as a national infection control policy in HTLV-1 high-prevalence countries. Author summary: Human T-cell leukemia virus type 1 (HTLV-1) is a carcinogenic retrovirus that causes adult T-cell leukemia-lymphoma (ATL) and HTLV-1-associated myelopathy-tropical spastic paraparesis (HAM/TSP), an unremitting and progressive neurological disorder that presents with spastic paraparesis, neurogenic bladder, sphincter dysfunction, and mild sensory disturbance in the lower extremities. HTLV-1 is endemic in the Southwestern part of Japan, sub-Saharan Africa, South America, the Caribbean area, foci in the Middle East, and Australia-Melanesia. Based on published seroprevalence rates, which are missing or sparse for up to 6/7th of the global population, an estimated 5 to 10 million people worldwide are infected with HTLV-1. Treatment of ATL and HAM/TSP is very difficult and no vaccine is available. HTLV-1 transmission patterns include mother-to-child transmission through breastfeeding, horizontal transmission through sexual intercourse, and direct contact transmission through blood. HTLV-1 antenatal screening is effective to prevent mother-to-child transmission of HTLV-1. The probability of mother-to-child transmission of HTLV-1 through long-term and short-term breastfeeding can be reduced from 20.3% and 7.4% to 2.5% by withholding breastfeeding. However, Japan is the only country in the world that has implemented HTLV-1 antenatal screening. This study demonstrates that HTLV-1 antenatal screening is cost-effective and has the potential to reduce the number of cases and deaths from ATL and HAM/TSP in HTLV-1 high prevalence countries.