Table 4.
Quality assessment of case-control studies using the Newcastle –Ottawa quality assessment scale
| Author, year | Selection | Comparability of cases and controlse | Exposure | |||||
|---|---|---|---|---|---|---|---|---|
| Case definition adequatea | Representativ-eness of the casesb | Selection of controlsc | Definition of controlsd | Ascertainment of exposuref | Same method of ascertainment for cases and controlsg | Non-response rateh | ||
| Mondul, 2012 [60] | ★ | ★ | ★ | ★ | ★★ | ★ | ★ | ★ |
| Boursi, 2015 [7] | B | ★ | ★ | ★ | ★★ | ★ | ★ | ★ |
a:★ = Requires some independent validation (e.g. > 1 person/record/time/process to extract information, or reference to primary record source such as X-rays or medical/hospital records; B = Record linkage (e.g. ICD codes in database) or self-report with no reference to primary record; C = No description
b:★All eligible cases with outcome of interest over a defined period of time, all cases in a defined catchment area, all cases in a defined hospital or clinic, group of hospitals, health maintenance organization, or an appropriate sample of those cases (e.g. random sample); B = Not satisfying requirements in part (★), or not stated
c:★Community controls (i.e. same community as cases and would be cases if had outcome; B = Hospital controls, within same community as cases (i.e. not another city) but derived from a hospitalized population; C = No description
d:★ If cases are first occurrence of outcome, then it must explicitly state that controls have no history of this outcome. If cases have new (not necessarily first) occurrence of outcome, then controls with previous occurrences of outcome of interest should not be excluded; B = No mention of history of outcome
e: A maximum of 2 stars can be allotted in this category: either cases and controls must be matched in the design and/or confounders must be adjusted for in the analysis. Statements of no differences between groups or that differences were not statistically significant are not sufficient for establishing comparability. Note: If the odds ratio for the exposure of interest is adjusted for the confounders listed, then the groups will be considered to be comparable on each variable used in the adjustment. Age = ★, other controlled factors = ★
f:★ = secure record (e.g. surgical records) or structured interview where blind to case/control status; C = interview not blinded to case/control status; D = written self-report or medical record only; E = no description
g:★ = yes; B = no.
h:★ = same rate for both groups; B = non-respondents described; C = rate different and no designation