Do we need audiogram-based prescriptions? A systematic review

Figures & data

Figure 1. Flow diagram of the selection process based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Note: n: number of studies; REM: real-ear measurement; HA: hearing aids.

Table 1. Study characteristics.

Fitting procedures	Author, publication year and setting	Participants	Intervention and comparator	Study design	Follow-up duration	Downs and Black’s quality assessment category
Comparative fitting procedure	Metselaar et al. (2008) Metselaar et al. (2009) The Netherlands University clinic	N = 254 (163 M; 91 F) Mean age = 71 years (29–95) PTA = 58 dB HL (31–103) HL type: predominantly or entirely SNHL Experienced HA users = 139 Unilateral HA = 58 New HA users = 115 Fitted using comparative procedure = 119	Intervention: COMPARATIVE Comparative fitting procedure (Several HAs were initially selected based on the participant’s hearing thresholds and specialist opinion, which was based on the participant’s performance on free-field speech intelligibility in quiet tasks and sound quality judgments, plus fine-tuning after 6 weeks). Comparator: NAL-RP + REM ^a	Between-group (participants were randomised and blinded to treatment. Outcome assessors were blinded to treatment allocation)	Metselaar et al. (2008) 12 weeks Metselaar et al. (2009) 6 months	Good Good
Client choice of presets	Humes et al. (2017) United States University clinic	Audiology best practice group N = 53 (28 M; 25 F) Mean age = 70 years (SD 6) PTA = 29 dB HL (SD 8) HL type: SNHL? New HA users Consumer-decided group N = 55 (27 M; 28 F) Mean age = 68 years (SD 6) PTA = 29 dB HL (SD 9) HL type: SNHL? New HA users Placebo group N = 55 (37 M; 18 F) Mean age = 70 years (SD 7) PTA = 27 dB HL (SD 8) HL type: SNHL? New HA users	Intervention 1: Client choice HAs pre-programmed in a 2 cc coupler to match the NAL-NL2 targets for three common audiograms Intervention 2: Placebo Zero dB insertion gain + REM Comparator: NAL-NL2 + REM ^b	Between-group (participants and outcome assessors were blinded and randomised to the allocated treatment)	6 weeks	Excellent
	Humes et al. (2019) United States University Clinic	N = 40 (20 M; 20 F) Mean age = 69.2 years (SD 6) HF PTA = 39 dB HL (SD 14) HL type: SNHL New HA users	Intervention: CLIENT CHOICE HAs pre-programmed in a 2 cc coupler to match the NAL-NL2 targets for three common audiograms Comparator: At the end of the experiment, all participants were given the opportunity to complete another follow-up trial where their HAs were programmed to audiology best practice (i.e., REM + NAL-NL2) ^b	Prospective sequential	Almost 4 weeks per condition	Good
	Urbanski et al. (2021) United States Community Clinic	N = 37 (20 M; 17 F) Mean age = 69 years (SD 8) PTA = 39 dB HL HL type: SNHL Experienced HA users = 13 New HA users = 24	Intervention: CLIENT CHOICE HAs pre-programmed in a KEMAR to match the NAL-NL2 targets of four common audiograms Comparator: NAL-NL2 + REM^c	Crossover (participants were blinded to the preset conditions and randomised to the order of the test conditions)	In the same session	Good
Self-fit approach	Reed et al (2019) United States University clinic	N = 9 (6 M; 3 F) Mean age = 63 years (SD 11) PTA = 29 dB HL (SD 6) HL type: SNHL New HA users = 9	Intervention 1: SELF-FIT Out-of-the-box condition (participants self-fit their DTCs using the manufacturer’s instructions only) Intervention 2: SELF-FIT Advanced-user condition (participants self-fit their DTCs with professional assistance) Comparator: Audiologist-fit condition (NAL-NL2 + REM)^d	Prospective sequential	In the same session	Fair
	Sabin et al. (2020) United States University clinic	Audiology best practice group: N = 37 (18 M; 19 F) Mean age = 62 years (SD 13) PTA = 28.8 dB HL (SD 9) HL type: 30 SNHL, 1 Mixed, 1 CHL, 5 NH Experienced HA users = 4 New HA users = 33 Self-fit group: N = 38 (18 M; 20 F) Mean age = 66 years (SD 12) PTA = 33 dB HL (SD 12) HL type: 34 SNHL, 1 Mixed, 3 NH. Experienced HA users = 10 New HA users = 28	Intervention: SELF-FIT Zero dB insertion gain + home-based self-adjustment of DTC’s gain, compression ratio, output limiter, and spectral tilt ( + NAL-NL2 + REM for preference comparison tasks) Comparator: NAL-NL2 + REM + additional fine-tuning^e	Between-group (participants were allocated on an alternating basis + within-group blinded preference and sound quality comparisons)	One month	Fair

Note: N: number of participants; M: male; F: female; SD: standard deviation; HFPTA: high-frequency pure-tone average; PTA: pure-tone average; HL: hearing level; SNHL: sensorineural hearing loss; CHL: conductive hearing loss; mixed: mixed hearing loss; HA: hearing aids; NAL-NL: National Acoustic Laboratories non-linear; REM: real-ear measurement; KEMAR: Knowles Electronic Mannequin for Acoustic Research; DTC: direct-to-consumer hearing device

^aHearing aids were adjusted as close as possible to the NAL-RP or NAL-NL2 targets with no additional details.

^bHearing aids were adjusted to match the NAL-NL2 65 dB SPL targets and the average real-ear aided response was within ± 5 dB of those targets for frequencies of up to 6 kHz.

^cHearing aids were adjusted to be within ± 3 dB of the NAL-NL2 65 dB SPL targets for frequencies up to 4 kHz.

^dThe NAL-NL2 targets were achieved for 66% of frequencies.

^eHearing aids were adjusted to be within ± 4 dB of the NAL-NL2 50 and 80 dB SPL targets for frequencies of up to 4 kHz

Figure 2. Summary of intervention categories and studies involved.

Figure 3. Forest plot of comparisons between client choice versus audiogram-based prescription, showing the SMD for each outcome. Squares represent the effect sizes or pooled effect estimates for each outcome, and whiskers denote the 95% confidence intervals around them. Note: n: number of studies; SMD: standardised mean difference; QoL: quality of life.

Figure 4. Forest plot of comparisons between the self-fit approach and audiogram-based prescription, showing the SMD or proportion difference for each outcome. Squares represent the effect sizes or pooled effect estimates for each outcome, and whiskers denote the 95% confidence intervals around them, except for listening preference, where the square represents the proportion difference and the whiskers denote the 95% confidence interval around it.

Metselaar, M., B. Maat, P. Krijnen, H. Verschuure, W. Dreschler, and L. Feenstra. 2008. “Comparison of Speech Intelligibility in Quiet and in Noise after Hearing Aid Fitting according to a Purely Prescriptive and a Comparative Fitting Procedure.” European Archives of Oto-Rhino-Laryngology 265 (9): 1113–1120. doi:10.1007/s00405-008-0596-x.

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