| 1. Study design appropriate? |
Ambiguously described, obviously bias inducing or unsuitable for the objectives and stated conclusions |
Possibly restricting but reflected in the scope of the objectives and the stated conclusions |
Planned to minimise bias and allow generalisability beyond the immediate scope of the objectives |
| 2. Adequate description of study participants? |
Little or no information given |
Incl/excl and other criteria such as term/ pre-term/ small for gestational age baby given in some way; at least two useful measures including measure of vitamin D status, ethnicity |
Incl/excl and other criteria such as term/ pre-term/ small for gestational age baby given in some way; at least three useful measures including measure of vitamin D status, ethnicity with measures of precision |
| 3. How is maternal vitamin D status measured? |
Dietary intake only or insufficient information |
Blood levels of circulating 25(OH)-vitamin D |
Blood levels of circulating 25(OH)-vitamin D, with details of precision, pick up of D2 and D3 and assay used |
| 4. Participants grouped according to Vitamin D status? |
Subjects divided and analysed in groups based on pre-existing vitamin D thresholds |
Subjects divided and analysed in groups according to Vitamin D level based on group characteristics |
Subjects not divided into groups according to Vitamin D level/ or grouped according to at threshold generated from the study |
| 5. Measurements of outcomes reliably ascertained? |
Inadequately explained or obviously unsuitable |
Adequate description and reliability/suitability of at least one of the following: instruments, technique/definition/protocol, people, place |
Detailed description and reliability of one and at least adequate description of the others |
| 6. Measurements of later outcomes objective? |
Subjective measure, eg bone or muscle pain, wheezing |
Ascertained from researcher examination |
Objective measure e.g. DXA, bone biopsy, lung function tests |
| 7. Measures of vitamin D intake/25(OH)-vitamin D level, bone outcomes rounded? |
Measures categorised or rounded very roughly, or if any clear evidence of rounding exists without explanation in the text |
Yes, but not by much |
No information given and no obvious reason to suspect rounding has occurred; or explicitly stated that measurements were not rounded |
| 8. Consideration for the effects of important confounding factors? (e.g. season, sunlight exposure, calcium intake, maternal compliance, infant feeding) |
One factor controlled for in tables, nothing for the others (NB whether they were measured or not is irrelevant) |
Most factors controlled for in tables, or fewer if one or more is adjusted for in regression |
Most factors adjusted for in regression |
| 9. Outcome assessment blind to maternal vitamin D status? |
N/A (cannot score −1 in this category) |
No details given |
Some details or statement given |
| 10. What proportion of the cohort was followed up? |
% FU is not given, unclear, or low (below 70%) |
% FU is low to average (70-90%) |
% FU is high (over 90%) |
| 11. Info on non-participants |
Very little or no information, or information given that is adequate but suggests a serious potential for bias |
Adequate information given, or information given that is very clear but suggests a moderate potential for bias |
Above average information given, none of which suggests a potential for bias |
| 12. Analysis rigorous and appropriate? |
No statistical analyses carried out (just tables or description) |
Tables of means & differences given with statistical tests (e.g. t-tests), or some regression but without clear/valid measure of association |
Regression (or similar technique) used which gives a valid measure of association (e.g. odds ratios, hazard ratios, relative risks) |
| 13. Sample size |
Extremely ambiguous, not given, or small (under 100) |
Average (100 to 1000) |
Large (over 1000) |
