Lifetime costs and benefits of primary prevention decreased progressively with increasing age: from 234,066 baht and 17.869 QALYs (age 45 years) to 104,115 baht and 6.730 QALYs (age 80 years) with do-nothing; from 550,571 baht and 18.413 QALYs to 219,738 baht and 6.975 QALYs with alendronate; from 519,782 baht and 18.300 QALYs to 208,924 baht and 6.930 QALYs with risedronate; from 611,129 baht and 18.231 QALYs to 244,479 baht and 6.849 QALYs with raloxifene; and from 1,437,414 baht and 18.452 QALYs to 557,321 baht and 7.015 QALYs with nasal calcitonin. Secondary prevention resulted in modest increases in costs and benefits compared with do-nothing.
Compared to do-nothing, incremental cost per QALY was lowest with alendronate (both primary and secondary prevention) followed by risedronate, raloxifene and nasal calcitonin. Primary prevention was generally more cost-effective than secondary prevention. Primary and secondary prevention were both more cost-effective in older women (up to 75 years of age). For example, the incremental cost per QALY with primary prevention alendronate was 496,286 baht in 50-year-old women and 471,811 baht in 80-year-old women. The corresponding figures for secondary prevention alendronate were 1,753,378 baht and 1,702,343 baht. All these estimates were far above the Thai cost-effectiveness threshold.
When considering systematic screening followed by alendronate treatment, OST and sequential DXA was the preferred strategy among the younger age groups (45 to 55 years). Differences between the combined strategy and DXA alone were negligible among older age groups (60 to 80 years). The incremental cost per QALY gained with OST and sequential DXA was lowest at 351,459 baht for 65-year-old women and highest at 753,229 baht for 45-year-old women.
The probabilistic analysis showed that do-nothing was the preferred strategy for both primary and secondary prevention regardless of patient age using the Thai Gross Domestic Product threshold (100,000 baht). Only at higher cost-effectiveness thresholds, treatment and/or screening might be cost-effective. These results were robust when changing assumptions on treatment compliance and discontinuation.