| Characteristic | Beser 2004 | Du 2004 | Duhamel 2000 | Strand 2002/2003 |
| Intervention 1 (I1) / intervention 2 (I2) / control 1 (C1) | I1. vitamin D 400 IU/day per os
C1. no placebo or other intervention | I1: fortified milk, averaged calcium 245 mg/day per os
I2: fortified milk, averaged calcium 245 mg/day per os, vitamin D3 133 IU/day per so
C1: no placebo or other intervention | I1. vitamin D3 100,000 IU every 3 months per os
C1. placebo | I1: promoting of exclusive breastfeeding from birth, supplementation of solid foods at age 5 months, weaning at 12 to 18 months, vitamin D 300 IU/day per os during the first 12 months, calcium 378 mg/day per os from age 5 months to 24 months
C1: no placebo or other intervention. |
| Randomised controlled clinical trial (RCT) | N | Y | Y | Y |
| Controlled clinical trial | ?
(presumed Y) | N | N | N |
| Prospective cohort study | N | N | N | N |
| Method of randomisation (specify) | N/A | ? | ? | ? |
| Unit of randomisation (individuals, cluster ‐ specify) | N/A | cluster (pupils of matched 3 x 3 schools) | individuals | cluster (children of 16 matched villages ) |
| Randomisation stratified for centres | N/A | N/A | ? | N/A |
| Randomisation ratio | N/A | ? | ? | ?
(intervention group: 14 villages, control group: 2 villages) |
| Concealment of allocation (specify) | N/A | ? | ? | ? |
| Study population representative of population | Y | ? | ?
(recruited from hospital) | Y |
| Method of selection of controls (specify) (*) | N/A | N/A | N/A | N/A |
| Patients in different groups form same population (*) | N/A | N/A | N/A | N/A |
| Exposed/unexposed over same period of time (*) | N/A | N/A | N/A | N/A |
| Ascertainment of group determination (specify) (*) | N/A | N/A | N/A | N/A |
| Ascertainment of outcome (specify) | direct measurement | direct measurement | direct measurement | direct measurement |
| Stated blinding (open; single, double, triple blind) | ? | ? | double | ? |
| Actual blinding: participant/parents | N/A | ? | Y | N/A |
| Actual blinding: caregiver / treatment administrator | N/A | ? | ? | N/A |
| Actual blinding: outcome assessor | ? | ? | ? | N |
| Actual blinding: others | ? | ? | ? | ? |
| Blinding checked: participant | ? | ? | ? | ? |
| Blinding checked: caregiver / treatment administrator | ? | ? | ? | ? |
| Blinding checked: outcome assessor | ? | ? | ? | ? |
| Primary endpoint defined | Y | N | N | Y |
| [n] of primary endpoint(s) | 1 | ? | ? | 1 |
| [n] of secondary endpoints | 0 | ? | ? | 2 |
| Total [n] of endpoints | 1 | 12
(no distinction made between primary and secondary outcomes) | 8
(no distinction made between primary and secondary outcomes) | 3 |
| Prior publication of study design | ? | ? | ? | ? |
| Power calculation | ? | ? | ? | ? |
| [n] participants per group calculated | ? | ? | ? | ? |
| Intention‐to‐treat analysis (ITT) | Y
(no summary statistic in analysis) | Y
(no summary statistic for rickets in analysis) | Y
(no summary statistic for rickets in analysis) | N
(based on analysed patients) |
| Per‐protocol‐analysis | N | N | N | N
(based on analysed patients) |
| ITT defined | N | N | N | N |
| Dealing with missing data | ? | ? | ? | ?
(imputing for birth weight which is not relevant for this review) |
| [n] of screened participants (I1/ I2 / C1 / total) | ? | ? | ? | ? |
| [n] of randomised/included participants (for primary endpoint) | I1: 302
C1: 374 | I1: 238
I2: 260
C1: 259 | I1: 32
C1: 34 | Total: 259 |
| [n] of participants finishing the study | I1: 293
C1: 369 | I1: 209
I2: 242
C1: 247 | I1: 32
C1: 31 | Total: 245 |
| [n] of patients analysed (for primary endpoint) | no summary statistic provided | no summary statistic for rickets provided | no summary statistic for rickets provided | I1: 183
C1: 46
Total: 229 |
| Description of discontinuing participants | N | Y | N | N |
| Drop‐outs (reasons explained) | N | Y | N | N |
| Withdrawals (reasons explained) | N | Y | N | N |
| Losses‐to‐follow‐up (reasons explained) | N | Y | N | N |
| [n] of participants who discontinued | 14 | 59 | 3 | 14 |
| [%] discontinuation rate | 2 | 8 | 5 | 5 |
| Discontinuation rate similar between groups | Y | Y | Y | Y |
| Differences [n] calculated to analysed patients | N/A | N/A | N/A | N/A |
| Adjustment for multiple outcomes / repeated measurements | N/A
no summary statistic provided | Y
no summary statistic for rickets provided | N/A
no summary statistic provided | Y |
| Baseline characteristics: clinically relevant differences | ? | ? | ? | Y
(more preterm born children in intervention group) |
| Treatment identical (apart from intervention) | ? | ? | ? | ? |
| Compliance measured | ? | Y | Y | Y |
| Other important covariates measured (specify) | ? | ? | ? | ? |
| Co‐morbidities measured | ? | ? | ? | ? |
| Co‐medications measured | ? | ? | ? | ? |
| Different length of follow‐up (taken into account) (*) | N/A | N/A | N/A | N/A |
| Loss of study patients taken into account | Y | Y | Y | Y |
| Specific doubts about study quality | N | N | N | N |
| Funding: commercial | ? | N | ? | N |
| Funding: non‐commercial | ? | Y | ? | Y |
| Publication status: peer review journal | Y | Y | Y | Y |
| Publication status: journal supplement | N | N | N | N |
| Publication status: abstract | N | N | N | N |
| Publication status: other | N | N | N | N |
| Symbols & abbreviations: Y = yes; N = no; ? = unclear; N/A = not applicable; I = intervention; C = control
(*) for prospective cohort studies only | | | | |
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