Blomberg Jensen 2018.
| Methods | Randomised single‐centre,triple‐blinded, clinical trial Duration of study: from January 2011 to August 2014, follow‐up 14 months |
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| Participants | Country: Denmark Population: men part of an infertile couple with impaired semen quality, N = 307 Mean age: 34.8 ± 6.6 years Inclusion criteria: impaired semen quality (determined by WHO criteria) and vitamin D insufficient (25 OHD level #50 nmol/L) Exclusion criteria: serious comorbidities |
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| Interventions | Vitamin D 1400 IU + calcium 500 mg (n = 151) plus vitamin D 300,000 IU oil once orally versus Placebo (n = 156) plus placebo oil once orally Duration of treatment: 150 days (5 months) |
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| Outcomes | Sperm parameters, reproductive hormones, live birth rate | |
| Notes | Power calculation performed. | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Low risk | Quote: "Infertile men were randomly assigned 1:1 (in blocks of 10) to either placebo or.." "Included men were given a specific trial identity number determined by minimization using the computer program Minim (21). Minimization was done using four groups based on serum 25OHD, sperm concentration, body mass index (BMI) and serum inhibin B" |
| Allocation concealment (selection bias) | Low risk | Quote: "Randomization and manufacture of the high initial dose of vitamin D and placebo were performed by Glostrup Apotek." |
| Blinding of participants and personnel (performance bias) All outcomes | Low risk | Quote: "triple‐blinded", "To avoid unblinding, the principal investigator gave the necessary clinical information to the sponsor, who had a list of numbers headed by X or Y. This ensured that both the principal investigator and the sponsor were unaware whether the patient was allocated to the vitamin D plus calcium (active) group or the placebo group (i.e., double blinding)." |
| Blinding of outcome assessment (detection bias) All outcomes | Low risk | Quote: "The trial remained blinded until all biochemical analyses, data handling, and statistical analyses by an independent statistician had been completed (i.e., triple blinding)." |
| Incomplete outcome data (attrition bias) All outcomes | Low risk | Quote: "Twenty men in the placebo group and 18 in the vitamin D plus calcium group were lost to follow‐up. In total, 269 of 307 men (87.6%) completed the study (Fig. 1). By counting returned tablets, it was evident that one man in the vitamin D group and three in the placebo group were noncompliant; however, all data from these four men were included in all the analyses." Quote: "Twenty‐nine of the 269 men completing the trial reported their partner was pregnant before start of the intervention, whereas five men lost their partner during the study period, leaving 235 with the possibility of effecting a pregnancy." ITT. No explanation given for lost to follow‐up? Therefore unclear risk |
| Selective reporting (reporting bias) | Low risk | All the outcomes from the protocol were reported |