Table 1

Methodological characteristics of included studies

Study characteristicNumber of studies (n=215)%
Study design
 Case series8338.6
Time point relative to outcomes
OCEBM Levels of Evidence
 Random sampled study (level 1)20.9
 Local, non-random sample (level 3)15069.8
 Case series (level 4)6329.3
Number of centres
 Single centre13864.2
 Hospital inpatients11854.9
 Emergency department attendances31.4
 Mixed treatment settings3918.1
 Not stated94.2
Diagnostic method
 Other laboratory technique188.4
 Clinical opinion62.8
 Mixed method94.2
 Not stated2210.2
Disease stage
 Acute illness14467
 After hospital discharge or recovery115.1
 Not stated5324.7
Ethical approval
 Not stated4721.9
Informed consent
 Not stated11854.9
NOS quality assessment
  • NOS, Newcastle–Ottawa Scale; OCEBM, Oxford Centre for Evidence-Based Medicine.