Precision-scored parental report questions and HL-scaled tympanometry as informative measures of hearing in otitis media 1 : Large-sample evidence on determinants and complementarity to pure-tone audiometry

Introduction: In otitis media with effusion (OME), hearing loss is a core sign/symptom and basis of concern, with absolute pure-tone threshold sensitivity (in dB HL) by air-conduction providing the default measure of hearing. However several fundamental problems limiting the value of HL measures in otitis media are insufficiently appreciated. To appraise the joint value and implications of multiple hearing measures towards more comprehensive hearing assessment in OM, we examine in two related articles the interrelations and common or diverging determinants of three measures, two of them objective: binaural HL, and ACET (the published quasi-continuous scaling of binaural tympanometry to HL). The third measure is partly subjective: parentally reported hearing difficulties (RHD-4); this is the precision-scored total of the 4 items selected for the OM8-30 general purpose questionnaire for parents in OM. Methods: The Eurotitis-2 study (Total N = 2886) internationally standardises OM8-30 and its OMQ-14 short form. The clinical and parent-response variables acquired cover many issues in diagnosis, symptomatology and impact of OM. Data acquisition was built upon routine clinic practice, enabling us also to document some properties of that practice, such as patterns of missing HL data. To address possible confounding or loss of representativeness from this, we investigated the implications of substituting tympanometry-based ACET for missing HL to give an HL/ACET hybrid. ACET is the mapping of categorical tympanometry to continuous HL. We simulated degrees of artificial missingness of HL up to 35% on the 1430 complete-data cases, using random deletion, with 1000-version bootstrapping. Correlations of this HL/ACET hybrid with pure (100%) HL then documented the degree of correlation retained under dilution of HL by an admixture of ACET; we also documented distribution shapes. For RHD-4, we then probed the determining influences on severity of score as an auditory disability measure, both background ones (from centre, age, sex, socio-economic status, length of history, diagnosis and season) and the two underlying objective hearing measures (HL, ACET). We ran these multiple regressions (GLMs), for representativeness and generality, both on 1430 complete-data cases (i.e. all 3 hearing variables present) and also on supplemented samples according to data required only for particular analyses (N increased by +56% to +68%). A further method of sample supplementation (by up to +96%) used the HL/ACET hybrid. Results: Sex made negligible difference in any analysis. The particular collaborating centre, age, season and diagnosis collectively influenced presence/absence of HL data very strongly. (Area under ROC 0.944). Socio-economic status did not influence HL presence; surprisingly, nor did RHD, ACET or length of history, after control for centre, age, diagnosis and season. Of the inter-correlations between hearing measures, only the one between ACET and RHD was influenced (slightly reduced) by the inclusion of cases without HL data. In the simulated substitutions, Pearson correlation of hybrid HL/ACET with true HL remained above 0.90 for substitution by ACET of up to 30% rate of artificially 'missing' HL. Centre differences were adequately summarised by simple absolute additive differences in mean local case severity. In the determinant models for RHD on the 1430 complete-data cases, HL and the set of background determinants collectively explained broadly similar proportions of RHD's variability, totalling 36.8% explained. On the larger maximum case samples, slightly less absolute variability was explicable than on complete-case data, but relative magnitudes of contribution from individual determinants, both background and hearing measures, remained similar. The expected mean differences in RHD between diagnoses (RAOM, OME, and combined) were found, but the patterns of background and objective measure influences determining RHD did not differ significantly between the diagnoses. Conclusions: (1) In the Eurotitis-2 database, descriptive differences in various background demographic and clinical measures between cases on whom HL data were obtained versus not, were only of material magnitude for length of history and reported hearing difficulties. Such descriptive differences are not necessarily bases of confounding, so using our framework of 6 background adjuster variables, (particular collaborating centre, age, season, diagnosis, socioeconomic status and length of history) we isolated the determinants of HL data presence. The first four listed strongly predicted HL data presence/absence so are sufficient to control analyses well for any bias or confounding by HL data presence.(2) Diagnoses as OME and combined (OME + RAOM) had higher probability of HL data being present relative to RAOM, indicating that HL acquisition is chiefly seen as confirming and quantifying hearing loss in (suspect) OME, not as ruling it out (e.g. in suspected RAOM). Given this, also using RHD and or ACET as pre-triage to efficiently target capacity and/or reduce costs and opportunity costs of acquiring HL would be rational, but there was no evidence of such precise use of initial hearing-related information to decide on HL acquisition.(3) The full six background variables explained comparable variance in Reported Hearing Difficulties (RHD) to what was explained by ACET, but not quite as much as by HL. Achieving a high percentage explained (32-37% from good models) required both classes of determinant to be entered as predictors. The pattern of background determining influences for RHD was largely stable, with or without objective measures as additional predictors, and on maximum or complete-data cases. Length of history strongly determines RHD for a given concurrent HL.(4) Accepting ACET as substitute where HL was missing in OM cases gave a sample-size enhancement of 17% in Eurotitis-2, with negligible difference in the pattern of determinants. This hybrid measure can be recommended as reasonable next-best when moderate percentages of HL data are missing.(5) The stable pattern of prediction of RHD suggests that our six background determinants provide a very promising low-cost yet comprehensive framework for determination. It hence offers pluripotent statistical adjustment against confounding, applicable to RAOM, OME and combined diagnoses in any analysis using this database. Claims that it thereby offers a sufficient framework for full European standardisation of all the scores from the OM8-30 questionnaire measures await parallel demonstrations for symptom areas other than RHD. As 25% of the variance in RHD severity can be explained by the six adjusters in our framework, none of the six variables should be omitted from acquisition and analytic use in future OM research.