Wilson 1980.

Methods	Double‐blinded It is unclear whether randomisation took place in this study and if so the methodological process has not been described
Participants	Setting: 2 different centres, conducted by 2 different investigators (Kaiser‐Permanente (K‐P), Oakland and Massachusetts Eye and Ear Infirmary (MEEI), Boston) Country: USA Total number: 123 (however only 119 were included in the analysis and 4 were excluded after the study (K‐P: 27 MEEI: 92)) Mean age: not known Male to female ratio: not mentioned Tinnitus (no. of patients): not mentioned Vertigo: K‐P 61% and MEEI 33% Duration of treatment: K‐P 10 days; MEEI 12 days
Interventions	K‐P Treatment group: oral methylprednisolone 12 days Control group: placebo MEEI Treatment group: oral dexamethasone 10 days Control group 1: placebo Control group 2: no treatment
Outcomes	Outcome measures: objective audiometry performed on admission, at 4 weeks and 3 months after the onset of hearing loss. A "complete recovery" was defined as recovery of hearing to within 10 dB of the unaffected ear speech reception score or averaged pure‐tone score (if loss was primarily in the high frequency range). A "partial recovery" was defined as recovery of hearing to within 50% or more of the unaffected ear's speech reception score or averaged pure‐tone score. A "no recovery" was defined as less than 50% recovery of hearing.
Notes	Quality score: C
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	There is evidence that the randomisation was inadequate and that this resulted in a selection bias. This is supported by the uneven distribution of the age, symptom of vertigo, audiogram types and number of the participants between the different treatment groups and between the 2 centres.
Allocation concealment (selection bias)	High risk	Allocation concealment was not mentioned and was assessed to be inadequate as 52 patients elected not to have treatment during the allocation process
Blinding (performance bias and detection bias) All outcomes	High risk	The control group that received no treatment was not blinded in this study as they knew they did not receive any tablets. There was no mention of the use of independent blinded assessors in this study. The study authors did not respond to our request for information relating to the degree of blinding.
Incomplete outcome data (attrition bias) All outcomes	High risk	The intention‐to‐treat analysis was not achieved as 4 patients were excluded from the study and 14 patients were reallocated to the control group after the initial allocation
Selective reporting (reporting bias)	High risk	The study authors then excluded the 34 patients with hearing loss of greater than 90 dB and 14 patients with mid‐frequency loss to perform a subgroup analysis of the remaining 74 patients
Other bias	High risk	There were problems with the study population. As the study was carried out in 2 different independent centres, there was heterogeneity of the population between the 2 centres. Furthermore, the types of steroids, dosage and duration of the steroid treatment were different between the 2 centres.

ISSHL: idiopathic sudden sensorineural hearing loss
 K‐P: Kaiser‐Permanente
 MEEI: Massachusetts Eye and Ear Infirmary