Table 2 Levels of evidence for the overall quality of the measurement property [24,25]

Strong

+++ or ---

Consistent findings in multiple studies of good methodological quality OR in one study of excellent methodological quality

Moderate

Consistent findings in multiple studies of fair methodological quality OR in one study of good methodological quality

Limited

+ or -

One study of fair methodological quality

Conflicting

+/−

Conflicting findings

Unknown

?

Only studies of poor methodological quality