An assessment of nucleic acid amplification testing for active mycobacterial infection

Stage 2: precision, size of effect and clinical importance

Statistical precision was determined using statistical principles. Small CIs and p-values give an indication as to the probability that the reported effect is real and not attributable to chance (NHMRC 2000). Studies need to be appropriately powered to ensure that a real difference between groups will be detected in the statistical analysis.

For intervention studies it was important to assess whether statistically significant differences between patients receiving intervention and comparator were also clinically important. The size of the effect needed to be determined, as well as whether the 95%CI included only clinically important effects.

The outcomes being measured in this report were assessed as to whether they were appropriate and clinically relevant (NHMRC 2000).