Ahn 2008.

Study characteristics
Methods	Non‐blinded, parallel‐group, randomised controlled trial with 14 days duration of treatment and a 3‐month duration of follow‐up
Participants	Setting: tertiary referral centre, Republic of Korea, February 2005 to March 2007 Sample size: Number randomised: 120 Number completed: 120 Primary/secondary therapy: primary therapy Participant (baseline) characteristics: age/sex (male, female)/hearing loss at start of therapy/start of treatment: Group I (combined): 48.6 ± 15.4 y/33 m, 27 f/74.3 ± 27.8 dB HL/6.5 ± 3.9 d Group II (systemic): 45.9 ± 14.7 y/31 m, 29 f/70.3 ± 21.3 dB HL/7.1 ± 4.1 d Inclusion criteria: SSNHL with acute onset of HL of > 30 dB in 3 contiguous frequencies, which may have occurred instantaneously or progressively over several days Exclusion criteria: medical or central nervous system conditions, including diabetes, hypertension, connective‐vascular disease, vestibular schwannoma, true vertigo with whirling type, and other conditions that could affect hearing recovery or selection of therapeutic methods
Interventions	General comparison: intratympanic plus systemic corticosteroids (combined therapy) versus systemic corticosteroids alone Intervention group (n = 60*): "combined therapy": intratympanic injection of dexamethasone, 5 mg/mL, 0.3 to 0.4 mL, 3 injections total, 1 injection every 2 days (first, third and fourth day) + systemic steroid therapy as in comparator group Comparator group (n = 60*): "systemic": 14‐day course of oral 48 mg methylprednisolone for 9 days, followed by tapering for 5 days Use of additional interventions (common to both treatment arms): vitamins and lipo‐prostaglandin E1 * intention‐to‐treat analysis
Outcomes	Primary outcome measure: Proportion of patients whose hearing is improved (criterion for improvement > 15 dB decrease and final < 75 dB HL in PTA/Siegel's criteria) Secondary outcomes: Frequency‐specific changes with pure tone audiometry Adverse events Primary endpoint for hearing threshold evaluation: 90 days Used PTA: 4PTA (0.5, 1, 2, 3 kHz)
Funding sources	No information available
Declarations of interest	No information provided
Notes	—
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Quote from protocol: "All patients are being allocated to one of two groups (ITD and control group) using randomizations table that is generated by random number generator (http://stattrek.com/statistics/random‐number‐generator.aspx)." Quote from protocol: "If a patients refuses to receive such treatment as allocated to him or her, the patient is going to be dropped from this study."
Allocation concealment (selection bias)	Unclear risk	Method of concealment is not described.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Open‐label trial, no blinding. Quote from protocol: "If a patients refuses to receive such treatment as allocated to him or her, the patient is going to be dropped from this study."
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Insufficient information to permit judgement (not mentioned).
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	No missing outcome data reported but patients could refuse allocated therapy.
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.