Tong 2021.

Study characteristics
Methods	Non‐blinded, parallel‐group randomised controlled trial with 10 days duration of treatment and 5 weeks duration of follow‐up
Participants	Setting: tertiary referral centre, China, October 2013 to June 2014 Sample size: Number randomised: 96 Number completed: 90 Primary/secondary therapy: primary therapy Participant (baseline) characteristics: age/sex (male, female)/baseline hearing loss at start of therapy/start of treatment: Group I (intratympanic): 40.2 ± 20.4 y/17 m, 13 f/68.1 ± 23.5 dB HL/4.9 ± 3.1 d Group II (systemic oral): 42.9 ± 19.4 y/15 m, 15 f/65.5 ± 20.5 dB HL/5.1 ± 3.4 d Group III (systemic intravenous): 44.9 ± 21.3 y/17 m, 13 f/66.49 ± 21.4 dB HL/5.1 ± 2.7 d Inclusion criteria: 1) unilateral ISSNHL of > 20 dB hearing level (HL) in least 3 consecutive frequencies, that occurred within ≤ 3 days without any identifiable cause, 2) a type A tympanogram, 3) a normal or almost‐normal HL in the contralateral ear (a 6‐frequency pure tone average [PTA] of < 30 dB HL), 4) an interval from the onset of symptoms to the beginning of therapy of < 14 days, 5) no history of disease in the affected ear, 6) no previous treatment, 7) age ≥ 18 yearsExclusion criteria: 1) the presence of a retrocochlear lesion or a neoplasm, 2) a history of chronic otitis media in the affected ear, 3) the presence of congenital cochlear malformations, 4) inadequate follow‐up after treatment (i.e. < 4 weeks), 5) recent use of ototoxic medications, 6) pregnancy, 7) a history of genetic sensorineural hearing loss, and 8) reported acoustic trauma or barotrauma
Interventions	General comparison: intratympanic versus systemic corticosteroid therapy Intervention group I (n = 30*): "intratympanic therapy": intratympanic 0.6 mL of 40 mg/mL methylprednisolone every second day for 10 days Comparator group I (n = 30*): "systemic therapy oral": oral methylprednisolone 0.8 mg/kg/day for the first 5 days and 8 mg/day for the next 5 days. Comparator group II (n = 30*): "systemic therapy intravenous": intravenous methylprednisolone 0.8 mg/kg/day for the first 5 days and 8 mg/day for the next 5 days. Use of additional interventions (common to all treatment arms): none *per protocol analysis
Outcomes	Primary outcome measure: Proportion of patients whose hearing is improved (criterion of improvement > 10 dB decrease in PTA) Secondary outcomes: Change in hearing threshold with pure tone audiometry Adverse events Primary endpoint for hearing threshold evaluation: 38 days Used PTA: 6PTA (0.25, 0.5, 1, 2, 4, 8 kHz)
Funding sources	The study was supported by the Education Department of Anhui Province (project No. 2014KJ: 120)
Declarations of interest	None declared
Notes	Only the treatment arm with oral corticosteroids was included in the meta‐analysis as the comparator to the intratympanic treatment arm because systemic groups in most of other studies were treated with oral corticosteroids.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Quote: "The randomization technique was a consecutive allocation by the visit sequence."
Allocation concealment (selection bias)	High risk	No allocation concealment possible because of the method of random sequence generation used.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Open‐label trial, no blinding.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "The outcome assessors were blinded as to the treatment method used".
Incomplete outcome data (attrition bias) All outcomes	Low risk	Reported moderate missing outcome data (5% to 10%) balanced in numbers across intervention groups (6.3%).
Selective reporting (reporting bias)	Low risk	No indication of selective reporting in the outcome parameters addressed by the review.
Other bias	High risk	No sample size calculation performed. Criteria for successful treatment was defined as > 30 dB HL decrease of PTA but used was > 10 dB HL decrease.