Assessment of research waste part 1: an exemplar from examining study design, surrogate and clinical endpoints in studies of calcium intake and vitamin D supplementation

Table 1 Classification of endpoints in 547 randomised controlled trials of vitamin D supplementation

Endpoint^a	Number of RCTs
Clinical endpoints
Fracture	18
Falls	17
Respiratory (eg asthma, COPD, URTI)	14
Musculoskeletal symptoms/Pain	11
Pregnancy outcomes	9
Tuberculosis	8
Multiple Sclerosis	7
Mood	6
SLE/Rheumatoid Arthritis	6
Other	41
Surrogate endpoints
Bone mineral density	57
25OHD only	49
HbA1c or measures of glycaemia	42
Blood pressure	38
Basic biochemistry	37
Bone turnover markers	31
25OHD, vitamin D metabolites and/or PTH only	24
Muscle Strength	16
Body weight	15
Physical performance tests	14
Vascular properties	7
Hepatitis C viral load	5
Lung function tests	4
Lipids	4
Other laboratory tests/assays	51
Other endpoints	16

Abbreviations: COPD chronic obstructive pulmonary disease, URTI upper respiratory tract infection, SLE Systemic lupus erythematosus, 25OHD 25 hydroxyvitamin D, PTH parathyroid hormone
^amany trials reported more than 1 endpoint in the abstract. The most clinically relevant endpoint was used for each study

ISSN: 1471-2288