Study design

The study involved a collaborative effort between the British Tinnitus Association (DS), Optimity Advisors (PB, CP), and an advisory group comprising members with expertise in tinnitus, from backgrounds in audiology (TK, Beth-Anne Culhane, Peter Byrom), ENT (DM), General Practice (CD), and research (DJH). It is reported according to the consolidated health economic evaluation reporting standards (CHEERS; [21]).

We mapped out the clinical pathways and treatment options used in people presenting to their GP with symptoms of tinnitus. Costs and probabilities of a patient receiving a particular treatment were attached to the various treatments along the different clinical pathways in order to generate an overall average NHS treatment cost. Clinical pathways were defined based on expert clinical opinion. The intention was to produce a framework which broadly describes existing treatment patterns in the NHS for tinnitus patients. The model developed therefore does not compare different treatment options for a population with given characteristics who have tinnitus. Rather, it provides a baseline for the overall treatment costs and health outcomes for the generality of patients with tinnitus, given a set of assumptions about the likelihood of being managed in various ways.

An Excel model was constructed mapping out the most common treatment pathways (involving education and reassurance, discharge and self-management, hearing aids, CBT, MTRT, clinical psychology) and a cohort of patients run through the model. The range of treatment options in the model is not exhaustive of all possibilities as there may be atypical local models, or patients may leave a tinnitus pathway to enter a mainstream mental health pathway or a non-NHS healthcare service. Variation in the severity of tinnitus was not explicitly incorporated into the model. The only feature distinguishing patients in terms of clinical presentation was candidacy for hearing aids which is determined only after referral from the GP for further assessment; note practices in the prescription of hearing aids for tinnitus management are highly variable, particularly where there is milder or higher frequency hearing loss, and are very much influenced by the clinical experience and opinion of individual audiologists [6]. Drawing on previous modelling work, tinnitus patients either did or did not experience an improvement in their condition. Those who experienced an improvement either successfully habituated (were ‘cured’) or did not successfully habituate. Those who did not successfully habituate were discharged to self-management. Those whose tinnitus does not improve can be referred on for further treatment.

Of the cohort of patients presenting to a GP for the first time, an estimated 30% are referred to ENT, 7% are referred to audiology and 63% receive education and reassurance from the GP and are not referred onwards [16]. Patients who are unsuccessful in habituating to their condition after seeing their GP are subsequently referred to ENT or audiology. Figures 1 and 2 present illustrative pathways captured by the model. Those undergoing evaluation by an audiologist or Ear Nose and Throat (ENT) specialist can be referred on for further treatment with modified tinnitus retraining therapy (MTRT) or cognitive behavioural therapy (CBT). For simplicity, Fig. 2 illustrates the treatment options for those not considered candidates for hearing aids. For those considered candidates for hearing aids on audiological/ENT assessment, the treatment options corresponding to MTRT and CBT are education and reassurance, hearing aids and maintenance, CBT plus hearing aids and maintenance and MTRT plus hearing aids and maintenance. We acknowledge that it may not be appropriate to allocate the entire cost of hearing aids to the treatment of tinnitus. However, given the difficulty of estimating the proportion attributable and in order not to bias the analysis in favour of treatment for tinnitus, we included the full cost of hearing aids, and conducted a sensitivity analysis to test the effect of this assumption.

Fig. 1 Clinical pathways. Initial presentation in the model starts with a General Practitioner (GP) consultation progressing to successive levels of onward referral, treatment, and ending with successful habituation (health benefit) or discharge to self-manage (no health benefit). ENT = ear nose and throat surgeon. Follow on treatment pathways are given in Fig. 2. Pathways are identified by letter (red text) and correspond to those in Table 1 Full size image

Fig. 2 Follow-on treatment pathways. Following on from ENT/Audiology examination and review tinnitus patients progress to successive levels of onward referral, treatment, and ending with successful habituation (health benefit) or discharge to self-manage (no health benefit). CBT = cognitive behaviour therapy; ENT = ear nose and throat surgeon; MTRT = modified tinnitus retraining therapy. For those considered candidates for hearing aids the treatment options corresponding to MTRT and CBT are education and reassurance, hearing aids and maintenance, CBT plus hearing aids and maintenance, and MTRT plus hearing aids and maintenance Full size image

It is assumed that the time from initial GP consultation to eventual successful habituation or discharge will be less than 12 months. Hence new treatment interventions will have all been exploited in the first year. Recurring costs are those associated with ongoing support. For example, the costs of hearing aid maintenance will be incurred over the lifetime of the patient. Annual costs were discounted at a rate of 3.5% per annum as used by NICE for health technology appraisals. The result is the present value of the lifetime cost for a patient following each of the defined clinical pathway options.

Sources of probabilities

The analysis draws on a number of sources of probabilities (Additional file 1). These include key journal publications, the results of a yet unpublished survey of the experiences of members of British Tinnitus Association (BTA), national statistics, and the clinical expert knowledge of the study team. Expert opinion was used to formulate a consensus, through discussion, on the current common clinical pathways followed by tinnitus patients.

Research evidence was used to estimate the following parameter values: the probability that tinnitus improves after CBT [22], the probability of receiving a hearing aid prescription [23], the probability that tinnitus improves after MTRT/CCBT and hearing aids [24], the probability of receiving a hearing aid [25], the probability of onward referral by GP and reattendance [16], the probability of improvement after hearing aid fitting or education and reassurance [26], the probability of receiving an audiology intervention, [15, 27, 28], CBT effectiveness [29], the probability of receiving MTRT [30], and the probability that tinnitus improves after CBT and hearing aids [31]. Member survey data were used to estimate values for another group of variables in the model such as the proportion of patients discharged rather than having onward referral by ENT. Remaining transition probabilities were obtained from a survey of experts, with disagreement (and logical inconsistencies) resolved by consensus.

Comparator

The implicit comparator was a patient who did not seek treatment for their condition and was assumed to incur zero tinnitus-related NHS treatment costs. In addition to treatment costs, a quality adjusted life year (QALY) gain was attributed to those patients who successfully habituated compared with those who are discharged at any stage and left to self-manage and relative to those who do not seek treatment. In the absence of good natural history data at the time of analysis, a hypothetical zero cost, zero QALY cohort at least provides a common comparator.

Modelling common tinnitus pathways

Probabilities

Table 1 gives illustrative examples of numbers following given pathways and the numbers of those habituating to their condition. Further description of these pathways is given in Additional file 2.

Table 1 Probabilities of overall distribution of 100 tinnitus patients to pre-defined patient pathways, successful habituation, and discharge to self-management Full size table

Costs

The direct NHS healthcare costs were captured or estimated for each clinical pathway including the costs of clinical consultations (GP, ENT, audiologist/hearing therapist, clinical psychologist), diagnostic assessments, and management options including sound devices (hearing aids, sound generators), pharmacotherapy, CBT, and MTRT. Unit costs and source references used in the model are given in Table 2 and Additional file 3. A number of assumptions related to how often costs are incurred were derived from expert knowledge and the BTA member survey. Examples of modelling assumptions are that:

50% of patients seen in audiology/ENT/audiovestibular medicine undergo an MRI scan;

hearing aids are reassessed and replaced every 4 years;

follow-up, repairs and maintenance of hearing aids are undertaken annually;

replacement of packs of 6 hearing aid batteries occurs 6 times a year;

one pair of hearing aids is issued to all patients using this management modality;

patients receive on average two GP appointments before they are first referred onwards;

patients treated by a Clinical Psychologist are seen twice in the initial year.

Table 2 Annual tinnitus-related treatment costs Full size table

The total annual healthcare cost of tinnitus in the NHS was calculated by multiplying the average cost per pathway by the proportion of patients per pathway in the model, and the estimated annual number of patients seeking NHS care for tinnitus in the UK.

Health outcomes

Health outcomes from a patient perspective were expressed in terms of quality adjusted life years (QALYs) per person where QALYs gained represent the number of years in good health which can be expected over the individual’s remaining lifetime (assumed to be 35 years) under NHS treatment relative to the comparator of no NHS treatment. Patients who successfully habituate to tinnitus gain QALYs, whereas patients who are discharged without treatment and self-manage in an undirected way have no QALY gain. An annual QALY gain of +0.02 (discounted QALY over 35 years = 0.4) was applied for all patients who successfully habituated to their tinnitus. No directly relevant studies on quality of life improvement suitable for calculating QALYs were found. However, an average ear disease pre-post management score on the Health Utilities Index mark 3 (Hui-3 [32]) has been reported by Swan et al. [33]. It was assumed that the pre-treatment quality of life applies over the lifetime for those who do not seek NHS care. The annual QALY gains in future years were discounted at a rate of 3.5% to determine a present value of lifetime health benefit.

Cost-effectiveness

Cost-effectiveness results were obtained by multiplying the relevant costs, QALYs and probabilities along each pathway considered. The assumptions underlying the cost-effectiveness results need to be borne in mind when interpreting the results presented below. As the main purpose of the study was to cost the range of possible pathways for the management of tinnitus, the cost-effectiveness results should be regarded as illustrative. We acknowledge the limitations of the analysis and highlight areas for further research in a later section.