Alex Hoetink ^1,2* Sarah Kaldenbach ³ Arnold Lieftink ^1,2 Huib Versnel ^1,2 Robert J. Stokroos ^1,2

• ¹ University Medical Center Utrecht, Utrecht, Netherlands
• ² Brain Center, University Medical Center Utrecht, Utrecht, Netherlands, Netherlands
• ³ Dutch Foundation for the Deaf and Hearing Impaired Child (NSDSK), Amsterdam, Netherlands

The results from different Cochrane studies justify considerable professional equipoise concerning different treatment options for tinnitus. In case of professional equipoise, Shared Decision Making (SDM) is an indispensable tool for guiding patients to the intervention that best fits their needs. To improve SDM we developed a method to assess the accuracy and utility of decisions made by tinnitus patients when freely choosing between different treatment options during their patient journey. The different treatment options were audiological care and psychosocial counseling. We developed a statistical model by combining Signal Detection Theory (SDT) with the Health Belief Model (HBM). HMB states that perceived severity of an illness is strongly related to sick-role behavior. As proxies for perceived severity, we selected hearing loss and Tinnitus Handicap Inventory (THI) score at baseline. Data was gathered in a prospective cohort of 145 adults referred for tinnitus care to an outpatient audiology clinic in the Netherlands. The participants were asked to decide freely about uptake of audiological care (provision of hearing aids with or without a sound generator) and uptake of psychosocial counseling. Logistic regression with Bayesian inference was used to determine the cumulative distribution functions and the probability density functions of true positive decisions and false positive decisions as function of hearing loss and baseline THI-score for both treatment options, respectively. Baseline THI-score drives decisions about psychosocial counseling and hearing loss drives decisions about audiological care. For decisions about audiological care the unbiased decision criterion is 37 dB(HL), meaning that a lenient decision criterion (likelihood ratio < 1) is adopted by patients with a hearing loss below 37 dB and a strict criterion (likelihood ratio > 1) by patients with a hearing loss exceeding 37 dB. For psychosocial counseling uptake the decision criterion is always strict, regardless of baseline THI-score. Combining SDT and HBM can help assess accuracy and utility of patient decisions and thus may provide valuable information that can help to improve SDM by combining patient related outcome measures, decision drivers, and perceived benefits and costs of a treatment.