Clinical heterogeneity in systematic reviews and health technology assessments: synthesis of guidance documents and the literature.
OBJECTIVE
The aim of this study was to synthesize best practices for addressing clinical heterogeneity in systematic reviews and health technology assessments (HTAs).


METHODS
We abstracted information from guidance documents and methods manuals made available by international organizations that develop systematic reviews and HTAs. We searched PubMed® to identify studies on clinical heterogeneity and subgroup analysis. Two authors independently abstracted and assessed relevant information.


RESULTS
Methods manuals offer various definitions of clinical heterogeneity. In essence, clinical heterogeneity is considered variability in study population characteristics, interventions, and outcomes across studies. It can lead to effect-measure modification or statistical heterogeneity, which is defined as variability in estimated treatment effects beyond what would be expected by random error alone. Clinical and statistical heterogeneity are closely intertwined but they do not have a one-to-one relationship. The presence of statistical heterogeneity does not necessarily indicate that clinical heterogeneity is the causal factor. Methodological heterogeneity, biases, and random error can also cause statistical heterogeneity, alone or in combination with clinical heterogeneity.


CONCLUSIONS
Identifying potential modifiers of treatment effects (i.e., effect-measure modifiers) is important for researchers conducting systematic reviews and HTAs. Recognizing clinical heterogeneity and clarifying its implications helps decision makers to identify patients and patient populations who benefit the most, who benefit the least, and who are at greatest risk of experiencing adverse outcomes from a particular intervention.
Danube University, Krems. gerald.gartlehner@donau-uni.ac.at
Gerald
G
Gartlehner
Suzanne L
SL
West
Alyssa J
AJ
Mansfield
Charles
C
Poole
Elizabeth
E
Tant
Linda J
LJ
Lux
Kathleen N
KN
Lohr
D019985:Benchmarking / Q000379:methods*; D015982:Bias; D020811:Biomedical Technology; D057186:Comparative Effectiveness Research; D003657:Decision Making; D006801:Humans; D017410:Practice Guidelines as Topic; D012196:Review Literature as Topic; D013673:Technology Assessment, Biomedical / Q000379:methods*