[1] European Medicines Agency. Guideline on the investigation of subgroups in confirmatory clinical trials ;

[2] Assmann SF, Pocock SJ, Enos LE, et al. Subgroup analysis and other (mis)uses of baseline data in clinical trials. Lancet 2000;355:1064–69 ;

[3] Fan J, Song F, Bachmann MO. Justification and reporting of subgroup analyses were lacking or inadequate in randomized controlled trials. J Clin Epidemiol 2019;108:17–25 10.1016/j.jclinepi.2018.12.009 [30557676]

[4] Bonaca MP, Bhatt DL, Cohen M, et al. Long-term use of ticagrelor in patients with prior myocardial infarction. N Engl J Med 2015;372:1791–800 10.1056/NEJMoa1500857 [25773268]

[5] Horton R. From star signs to trial guidelines. The Lancet 2000;355:1033–34 10.1016/S0140-6736(00)02031-6 [10744086]

[6] Rothwell PM. Subgroup analysis in randomised controlled trials: importance, indications, and interpretation. The Lancet 2005;365:176–86 10.1016/S0140-6736(05)17709-5

[7] Robert C, Karaszewska B, Schachter J, et al. Improved overall survival in melanoma with combined dabrafenib and trametinib. N Engl J Med 2015;372:30–39 10.1056/NEJMoa1412690 [25399551]

[8] Brookes ST, Whitely E, Egger M, et al. Subgroup analyses in randomized trials: risks of subgroup-specific analyses; power and sample size for the interaction test. J Clin Epidemiol 2004;57:229–36 ;

[9] Brookes ST, Whitley E, Peters TJ, et al. Subgroup analyses in randomised controlled trials: quantifying the risks of false-positives and false-negatives. Health Technol Assess 2001;5:1–56 10.3310/hta5330 [11701102]

[10] Hernández AV, Boersma E, Murray GD, et al. Subgroup analyses in therapeutic cardiovascular clinical trials: are most of them misleading? Am Heart J 2006;151:257–64 10.1016/j.ahj.2005.04.020 [16442886]

[11] Kasenda B, Schandelmaier S, Sun X, et al. Subgroup analyses in randomised controlled trials: cohort study on trial protocols and journal publications. BMJ-BRITISH MEDICAL JOURNAL 2014;349:g4539 10.1136/bmj.g4539 [25030633]

[12] Parker AB, Naylor CD. Subgroups, treatment effects, and baseline risks: some lessons from major cardiovascular trials. Am Heart J 2000;139:952–61 10.1067/mhj.2000.106610 [10827374]

[13] Sun X, Briel M, Busse JW, et al. Credibility of claims of subgroup effects in randomised controlled trials: systematic review. BMJ 2012;344:e1553 10.1136/bmj.e1553 [22422832]

[14] Herbst RS, Baas P, Kim D-W, et al. Pembrolizumab versus docetaxel for previously treated, PD-L1-positive, advanced non-small-cell lung cancer (KEYNOTE-010): a randomised controlled trial. The Lancet 2016;387:1540–50 10.1016/S0140-6736(15)01281-7 [26712084]

[15] Cappuzzo F, Ciuleanu T, Stelmakh L, et al. Erlotinib as maintenance treatment in advanced non-small-cell lung cancer: a multicentre, randomised, placebo-controlled phase 3 study. The Lancet Oncology 2010;11:521–29 10.1016/S1470-2045(10)70112-1

[16] Naggara O, Raymond J, Guilbert F, et al. The problem of subgroup analyses: an example from a trial on ruptured intracranial aneurysms. AJNR Am J Neuroradiol 2011;32:633–36 10.3174/ajnr.A2442 [21436333]

[17] Mok TS, Wu Y-L, Thongprasert S, et al. Gefitinib or carboplatin-paclitaxel in pulmonary adenocarcinoma. N Engl J Med 2009;361:947–57 10.1056/NEJMoa0810699 [19692680]

[18] Maemondo M, Inoue A, Kobayashi K, et al. Gefitinib or chemotherapy for non-small-cell lung cancer with mutated EGFR. N Engl J Med 2010;362:2380–88 10.1056/NEJMoa0909530 [20573926]

[19] Tanniou J, van der Tweel I, Teerenstra S, et al. Subgroup analyses in confirmatory clinical trials: time to be specific about their purposes. BMC Med Res Methodol 2016;16:20 10.1186/s12874-016-0122-6 [26891992]

[20] Kent DM, Paulus JK, van Klaveren D, et al. The Predictive Approaches to Treatment effect Heterogeneity (PATH) Statement. Ann. Intern. Med. 2020;172:35–45 10.7326/M18-3667 [31711134]

[21] Kaiser LD. Stratification of randomization is not required for a pre-specified subgroup analysis. Pharm Stat 2013;12:43–47 10.1002/pst.1550 [23281052]

[22] Horby P, Lim WS, Emberson JR, et al. Dexamethasone in Hospitalized Patients with Covid-19 - Preliminary Report. N Engl J Med 2020 10.1056/NEJMoa2021436 [32678530]

[23] Lipsky AM, Gausche-Hill M, Vienna M, et al. The importance of "shrinkage" in subgroup analyses. Annals of emergency medicine 2010;55:544-552.e3 10.1016/j.annemergmed.2010.01.002 [20138396]

[24] Aronson D. Subgroup analyses with special reference to the effect of antiplatelet agents in acute coronary syndromes. Thromb Haemost 2014;112:16–25 10.1160/TH13-09-0801 [24599493]

[25] Sleight P. Subgroup analyses in clinical trials - fun to look at, but don't believe them! Curr Control Trials Cardiovasc Med 2000;1:25–27 ;