Background/Purpose:

Diagnosis (dx) of systemic lupus erythematosus (SLE) is made via a combination of clinical and laboratory examinations; the sensitivity and specificity (S&S) of standard diagnostic tests (SDTs) (i.e.: ANA and antibodies to dsDNA, Smith, Ro/SSA, La/SSB, centromere, Jo-1, Scl-70, and CCP), are reported to be 83% & 76%, respectively (Putterman et al, 2014). A multivariate assay panel (MAP) combining biomarkers, complement C4d activation products on erythrocytes & B cells, with SDTs, yields improved dx performance with a S&S of 80% & 86%, respectively (Putterman et al, 2014). We evaluated the payer budget impact of SLE dx using MAP compared to SDTs.

Methods:

We modeled a health plan of 1 million enrollees, with 0.1% suspected of SLE. SLE dx among suspected SLE patients was 9.2% (Djikstra et al, 1999). The MAP arm assumed 80% /20% of suspected SLE patients were tested with MAP/SDTs, compared to 100% SDT testing in SDT arm.  Based on improved MAP performance, the hazard ratio for the assumed dx rate compared to SDTs was 1.74, (71, 87, 90, and 91% of the suspected who develop SLE will be diagnosed in years 1 – 4 compared to 53, 75, 84, and 88% with SDTs). Increased MAP performance relative to SDTs should result in earlier dx of SLE, reduction in disease severity at dx, and a longer period of time in less severe disease states (Oglesby et al, 2014) with associated lower costs. Pre-SLE dx claims-based cost data was used to estimate recurring direct costs for undiagnosed patients, and a weighted average of post-dx direct cost data for mild, moderate, and severe SLE were obtained from the literature (Garris, 2014) for SDTs, which was re-weighted to reflect the MAP scenario (Table 1).

Results:

Total 4-year pre- and post- dx direct medical cost for suspected SLE patients tested with MAP were $58,919,462 compared to $61,174,818 by SDTs (Table 2). Total 4-year average cost savings per suspected SLE patient tested with MAP were $2,256 (Table 2). Reduced inpatient hospital admissions were the biggest driver of cost savings ($581,728 in yr 1). In a one-way sensitivity analysis, the percentage of SLE dx among those suspected of SLE and specificity of MAP had the largest impact on average annual cost savings (respective savings of $16 and $15 per 1% absolute increase in percentage of SLE among those suspected of SLE and MAP specificity).

Conclusion:

Incorporating MAP into SLE dx results in total 4-year direct cost savings of $2,255,356 ($2,256 per suspected SLE patient) and year 1 savings of $711 per suspected SLE patient. Further, by facilitating earlier dx of SLE at a less severe disease state, it is anticipated that MAP will enhance patient outcomes.

Tables and Figures: