TY - JOUR
T1 - Comparison between treatment effects in a randomised controlled trial and an observational study using propensity scores in primary care
AU - Stuart, Beth L.
AU - Grebel, Louise E.N.
AU - Butler, Christopher C.
AU - Hood, Kerenza
AU - Verheij, Theo J.M.
AU - Little, Paul
N1 - Funding Information:
Funding was from the European Commission Framework Programme 6 (LSHM-CT-2005-518226): Eudract-CT 2007-001586-15 UKCRN Portfolio ID 4175 ISRCTN52261229 FWO G.0274.08N. The researchers are independent of all funders. The work in the UK was also supported by the National Institute for Health Research. In Barcelona, the work was supported by: 2009 SGR 911, Ciber de Enfermedades Respiratorias (Ciberes CB06/06/0028); the Ciberes is an initative of the ISCIII. In Flanders (Belgium), this work was supported by the Research Foundation — Flanders (FWO; G.0274.08N). The South East Wales Trials Unit is funded by the National Institute for Social Care and Health Research.
Publisher Copyright:
© British Journal of General Practice.
PY - 2017/9/1
Y1 - 2017/9/1
N2 - Background Although randomised controlled trials (RCTs) are considered 'gold standard' evidence, they are not always feasible or appropriate, and may represent a select population. Observational studies provide a useful alternative to enhance applicability, but results can be biased due to confounding. Aim To explore the utility of propensity scores for causal inference in an observational study. Design and setting Comparison of the effect of amoxicillin on key outcomes in an international RCT and observational study of lower respiratory tract infections. Method Propensity scores were calculated and applied as probability weights in the analyses. The adjusted results were compared with the effects reported in the RCT. Results Groups were well balanced in the RCT but significantly imbalanced in the observational study, with evidence of confounding by indication: patients receiving antibiotics tended to be older and more unwell at baseline consultation. In the trial duration of symptoms (hazard ratio 1.06, 95% CI = 0.96 to 1.18) and symptom severity (-0.07, 95% CI = -0.15 to 0.007) did not differ between groups. Weighting by propensity score in the observational study resulted in very similar estimates of effect: duration of symptoms (hazard ratio 1.06, 95% CI = 0.80 to 1.40) and difference for symptom severity (-0.07, 95% CI = -0.34 to 0.20). Conclusion The observational study, after conditioning on propensity score, echoed the trial results. Provided that detailed information is available on potential sources of confounding, effects of interventions can probably be assessed reasonably well in observational datasets, allowing them to be more directly compared with the results of RCTs.
AB - Background Although randomised controlled trials (RCTs) are considered 'gold standard' evidence, they are not always feasible or appropriate, and may represent a select population. Observational studies provide a useful alternative to enhance applicability, but results can be biased due to confounding. Aim To explore the utility of propensity scores for causal inference in an observational study. Design and setting Comparison of the effect of amoxicillin on key outcomes in an international RCT and observational study of lower respiratory tract infections. Method Propensity scores were calculated and applied as probability weights in the analyses. The adjusted results were compared with the effects reported in the RCT. Results Groups were well balanced in the RCT but significantly imbalanced in the observational study, with evidence of confounding by indication: patients receiving antibiotics tended to be older and more unwell at baseline consultation. In the trial duration of symptoms (hazard ratio 1.06, 95% CI = 0.96 to 1.18) and symptom severity (-0.07, 95% CI = -0.15 to 0.007) did not differ between groups. Weighting by propensity score in the observational study resulted in very similar estimates of effect: duration of symptoms (hazard ratio 1.06, 95% CI = 0.80 to 1.40) and difference for symptom severity (-0.07, 95% CI = -0.34 to 0.20). Conclusion The observational study, after conditioning on propensity score, echoed the trial results. Provided that detailed information is available on potential sources of confounding, effects of interventions can probably be assessed reasonably well in observational datasets, allowing them to be more directly compared with the results of RCTs.
KW - Antibiotics
KW - Observational study
KW - Primary health care
KW - Propensity score
KW - Randomised controlled trial respiratory tract infection
UR - http://www.scopus.com/inward/record.url?scp=85034270160&partnerID=8YFLogxK
U2 - 10.3399/bjgp17X692153
DO - 10.3399/bjgp17X692153
M3 - Article
AN - SCOPUS:85034270160
SN - 0960-1643
VL - 67
SP - e643-e649
JO - British Journal of General Practice
JF - British Journal of General Practice
IS - 662
ER -