Dawson 1990.

Methods	Randomised controlled trial Duration of study: 4 weeks
Participants	Country: USA Population: men with sperm agglutination, N = 30 Mean age: range 25 to 45 years Inclusion criteria: sperm agglutination over 25%, negative sperm antibodies, physically normal, no inflammatory disease Exclusion criteria: unclear
Interventions	Ascorbic acid (vitamin C) 1000 mg (n = 10) versus Ascorbic acid (vitamin C) 200 mg (n = 10) versus Placebo (n = 10) Duration of treatment: 3 weeks
Outcomes	Seminal parameters
Notes	Placebo numbers split by 2. Data were given in SE converted to SD New comment 2018: progressive forward motility instead of total motility, data total sperm motility moved to outcome progressive sperm motility
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "By random selection, three groups of 10 subjects each.."
Allocation concealment (selection bias)	Unclear risk	Not mentioned
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "Each subject was told he was receiving AA and expected improvement in sperm quality"
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not mentioned
Incomplete outcome data (attrition bias) All outcomes	Low risk	No dropouts
Selective reporting (reporting bias)	Unclear risk	All specified outcomes were reported. No protocol available.