Conclusions
In summary, subgroup analysis in phase III haematology malignancies RCTs are of poor quality, identifying flaws already described in other areas of study, such as the great number of subgroups reported, inappropriate a priori specification and the underused of interaction test.
Although not as frequent as in other areas, subgroup claims credibility was low. Most claims do not meet critical criteria; therefore, clinicians should interpret these results with caution. Subgroup analysis should be carried out due to the potential information they can provide, however researchers should be more cautious before claiming the existence of a subgroup effect.