Smith 1999.
| Study characteristics | ||
| Methods | Factorial design, individually randomised trial conducted in Belize | |
| Participants |
Eligibility: children aged 2.2–5.5 years Excluded: children with fever or serious respiratory illness Sample: 51 children. Mean age 46.3 months |
|
| Interventions | 4 intervention groups Experimental group I: vitamin A 10,000 IU Experimental group II: zinc 70 mg Experimental group III: vitamin A 10,000 IU + zinc 70 mg Control group: placebo Study duration: 6 months |
|
| Outcomes | Vitamin A serum level | |
| Notes | ||
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Unclear risk |
Quote: "The children selected were randomly assigned to receive one of the following supplements once per week: placebo; Zn, 70 mg as Zn gluconate; vitamin A, 3030 RE as retinyl palmitate; or a combination of vitamin A and Zn". Comment: stated to be randomised, but no further data reported. |
| Allocation concealment (selection bias) | Unclear risk | Comment: insufficient details provided. |
| Blinding (performance bias and detection bias) Blinding of participants | Unclear risk |
Quote: "Supplements were ingested orally in an orange flavoured powder (10 g), Tangt (Kraft General Foods Inc, White Plains, NY 10625) prepared as a beverage dissolved in approximately 120 mL of water". Comment: stated to be "double‐blind" in the article keywords, but there appeared to be no details about blinding methods in the text. The intervention (or no intervention in the placebo group) were diluted in the same solution, so presumably all groups were identical. |
| Blinding (performance bias and detection bias) Blinding of provider | Unclear risk | Comment: not adequately reported. |
| Blinding (performance bias and detection bias) Blinding of outcome assessor | Unclear risk | Comment: not adequately reported. |
| Incomplete outcome data (attrition bias) | Unclear risk | Comment: insufficient details provided; losses not accounted for by group and small sample size made this especially relevant. |
| Selective reporting (reporting bias) | Unclear risk | Comment: did not reference a protocol or trial registration number and did not state that all measured outcomes were reported. |
| Other bias | Unclear risk | Comment: insufficient details provided. |