Table 1.
Clinical and cost parameters used in MAP arm and SDLTs arm
| Parameter | MAP Arm | SDLTs Arm | Sources/Notes on Derivation |
|---|---|---|---|
| Clinical parameters | |||
| % with SLE among those with suspected SLE | 9.2% | 9.2% | Dijkstra et al (4) |
| % with RA, SS, or other CTD among those with suspected SLE | 58% | 58% | Dijkstra et al (4) |
| Ratio of RA to SS | 1.44 | 1.44 | Dijkstra et al (4); RA and SS represent CTDs with high and low postdiagnosis costs, respectively |
| Sensitivity | 80% | 83% | Putterman et al (11) |
| Specificity | 86% | 76% | Putterman et al (11) |
| Diagnosed with definitive CTD within year 1 | 71% | 53% | Hazard ratio of 1.74 for the assumed diagnosis rate applied a |
| Diagnosed with definitive CTD within year 2 | 87% | 75% | Hazard ratio of 1.74 for the assumed diagnosis rate applied a |
| Diagnosed with definitive CTD within year 3 | 90% | 84% | Hazard ratio of 1.74 for the assumed diagnosis rate applied a |
| Diagnosed with definitive CTD within year 4 | 91% | 88% | Hazard ratio of 1.74 for the assumed diagnosis rate applied a |
| Cost parameter | |||
| Incremental cost of MAP vs SDLTs | $108 | N/A | Medicare allowable CY 2017 |
| Average prediagnosis cost per patient with SLE/year | $24 593 | $24 593 | MarketScan Data Claims Analysis |
| Average prediagnosis cost per patient without SLE/year b | $17 495 | $17 495 | MarketScan Data Claims Analysis |
| Ratio of prediagnosis costs per patient without SLE: prediagnosis costs per patient with SLE | 0.7114 | 0.7114 | Costs for patient with newly diagnosed SLE without nephritis and matched control, Li et al (17) |
| Average per patient cost for mild SLE/year | $7021 | $7021 | Garris et al (19) |
| Average per patient cost for moderate SLE/year | $14 516 | $14 516 | Garris et al (19) |
| Average per patient cost for severe SLE/year | $47 252 | $47 252 | Garris et al (19) |
| Average per‐year postdiagnosis cost for true‐positive c , d | $18 123 | $19 578 | Garris et al (19) |
| Average true‐negative per year postdiagnosis cost d | $10 375 | $10 375 | Kawatkar et al (20) and McDonald et al (21). Assume true‐negative managed as a mix of RA/SS |
| Average false‐positive per‐year postdiagnosis cost d | $14 441 | $14 441 | Garris et al (19). Assume false‐positive managed like SLE, RA managed like mild/moderate/severe SLE, and SS managed like mild SLE |
| Average false‐negative per‐year postdiagnosis cost d | $14 516 | $14 516 | Garris et al (19). Assume false negative managed similarly to Moderate Disease severity |
Abbreviations: CTD, connective tissue disease; MAP, multivariate assay panel; RA, rheumatoid arthritis; SDLT, standard diagnostic laboratory test; SLE: systemic lupus erythematosus; SS, Sjogren’s syndrome.
The diagnosis rate was converted into a base case hazard function to estimate the percent diagnosed for each year in the model (Figure 1).
Prediagnosis costs for patients who are SLE negative are based on the factor of 0.7114 from Li et al (17).
Case severity mix for SDLTs and associated postdiagnosis costs in each severity (ie, mild, moderate, and severe) category were sourced from Garris et al (19). SDLTs: mild SLE: 26% at $7021; moderate SLE: 52% at $14 516; severe SLE: 22% at $47 252. MAP: Costs for all severity grades of SLE are equivalent to those in the SDLTs arm; however, weights are adjusted: mild SLE, 36%; moderate SLE, 45%; and severe SLE, 19%
False‐positives: individuals without SLE who were diagnosed with SLE; false‐negatives: individuals who were incorrectly diagnosed as not having SLE; true‐negative: individuals who were correctly diagnosed as not having SLE; true‐positive: individuals who were correctly diagnosed as having SLE