Patient and societal value functions for the testing morbidities index.

BACKGROUND

We developed preference-based and summated scale scoring for the Testing Morbidities Index (TMI) classification, which addresses short-term effects on quality of life from diagnostic testing before, during, and after testing procedures.

METHODS

The two TMI preference functions use multiattribute value techniques; one is patient-based and the other has a societal perspective, informed by 206 breast biopsy patients and 466 (societal) subjects. Because of a lack of standard short-term methods for this application, we used the visual analog scale (VAS). Waiting tradeoff (WTO) tolls provided an additional option for linear transformation of the TMI. We randomized participants to 1 of 3 surveys: The first derived weights for generic testing morbidity attributes and levels of severity with the VAS; a second developed VAS values and WTO tolls for linear transformation of the TMI to a "dead-healthy" scale; the third addressed initial validation in a specific test (breast biopsy). The initial validation included 188 patients and 425 community subjects. Direct VAS and WTO values were compared with the TMI. Alternative TMI scoring as a nonpreference summated scale was included, given evidence of construct and content validity.

RESULTS

The patient model can use an additive function, whereas the societal model is multiplicative. Direct VAS and the VAS-scaled TMI were correlated across modeling groups (r = 0.45-0.62). Agreement was comparable to the value function validation of the Health Utilities Index 2. Mean absolute difference (MAD) calculations showed a range of 0.07-0.10 in patients and 0.11-0.17 in subjects. MAD for direct WTO tolls compared with the WTO-scaled TMI varied closely around 1 quality-adjusted life day.

CONCLUSIONS

The TMI shows initial promise in measuring short-term testing-related health states.