Send to

Choose Destination
Trials. 2018 Jul 16;19(1):382. doi: 10.1186/s13063-018-2774-5.

Preventing false discovery of heterogeneous treatment effect subgroups in randomized trials.

Author information

Quantitative Sciences Unit, Stanford University School of Medicine, 1070 Arastradero Road #3C3104, MC 5559, Palo Alto, California, 94304, USA.
Stanford Prevention Research Center, Stanford University School of Medicine, Medical School Office Building, Room 318,1265 Welch Road, MC 5411, Stanford, CA, 94305, USA.
Departments of Medicine and of Health Research and Policy, Center for Primary Care and Outcomes Research and Center for Population Health Sciences, Stanford University School of Medicine, 1070 Arastradero Road, Office 282 MC 5560, Palo Alto, CA, 94304, USA.



Heterogeneous treatment effects (HTEs), or systematic differences in treatment effectiveness among participants with different observable features, may be important when applying trial results to clinical practice. Current methods suffer from a potential for false detection of HTEs due to imbalances in covariates between candidate subgroups.


We introduce a new method, matching plus classification and regression trees (mCART), that yields balance in covariates in identified HTE subgroups. We compared mCART to a classical method (logistic regression [LR] with backwards covariate selection using the Akaike information criterion ) and two machine-learning approaches increasingly applied to HTE detection (random forest [RF] and gradient RF) in simulations with a binary outcome with known HTE subgroups. We considered an N = 200 phase II oncology trial where there were either no HTEs (1A) or two HTE subgroups (1B) and an N = 6000 phase III cardiovascular disease trial where there were either no HTEs (2A) or four HTE subgroups (2B). Additionally, we considered an N = 6000 phase III cardiovascular disease trial where there was no average treatment effect but there were four HTE subgroups (2C).


In simulations 1A and 2A (no HTEs), mCART did not identify any HTE subgroups, whereas LR found 2 and 448, RF 5 and 2, and gradient RF 5 and 24, respectively (all false positives). In simulation 1B, mCART failed to identify the two true HTE subgroups whereas LR found 4, RF 6, and gradient RF 10 (half or more of which were false positives). In simulations 2B and 2C, mCART captured the four true HTE subgroups, whereas the other methods found only false positives. All HTE subgroups identified by mCART had acceptable treated vs. control covariate balance with absolute standardized differences less than 0.2, whereas the absolute standardized differences for the other methods typically exceeded 0.2. The imbalance in covariates in identified subgroups for LR, RF, and gradient RF indicates the false HTE detection may have been due to confounding.


Covariate imbalances may be producing false positives in subgroup analyses. mCART could be a useful tool to help prevent the false discovery of HTE subgroups in secondary analyses of randomized trial data.


Classification and regression trees; Decision support tool; Heterogeneous treatment effects; Matching

[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for BioMed Central Icon for PubMed Central
Loading ...
Support Center