Objective To find and review published papers researching surgeons’ effects on patients’ physical health. Clinical outcomes of surgery patients with similar prognoses cannot be fully explained by surgeon skill or experience. Just as there are “hospital” and “psychotherapist” effects, there may be “surgeons” effects that persist after controlling for known variables like patient health and operation riskiness. Methods Cohort studies and randomized controlled trials (RCTs) of any surgical intervention, which, after multivariate adjustment, either showed proportion of variance in patients’ physical health outcomes due to surgeons (random effects) or graded surgeons from best to worst (fixed effects). Studies with <15 surgeons or only ascribing surgeons’ effects to known variables excluded. Medline, PubMed, Embase, and PsycINFO were used for search until June 2020. Manual search for papers referring/referred by resulting studies. Risk of bias assessed by Cochrane risk-of-bias tool and Newcastle–Ottawa Scale. Results Included studies: 52 cohort studies and three RCTs of 52,436+ surgeons covering 102 outcomes (33 unique). Studies either graded surgeons from best to worst or calculated the intra-class correlation coefficient (ICC), the percentage of patients’ variation due to surgeons, in diverse ways. Sixteen studies showed exceptionally good and/or bad performers with confidence intervals wholly above or below the average performance. ICCs ranged from 0 to 47%, median 4.0%. There are no well-established reporting standards; highly heterogeneous reporting, therefore no meta-analysis. Discussion Interpretation: There is a surgeons' effect on patients’ physical health for many types of surgeries and outcomes, ranging from small to substantial. Surgeons with exceptional patient outcomes appear regularly even after accounting for all known confounding variables. Many existing cohort studies and RCTs could be reanalyzed for surgeons’ effects especially after methodological reporting guidelines are published. Conclusion In terms of patient outcomes, it can matter which surgeon is chosen. Surgeons with exceptional patient outcomes are worth studying further.

Purpose Despite billions of doctor visits worldwide each year, little is known on whether doctors themselves affect patients’ physical health after accounting for intervention and confounders such as patients’ and doctors’ data, hospital effects, nor how strong that doctors’ effect is. Knowledge of surgeons’ and psychotherapists’ effects exists, but not for 102 other medical specialties notwithstanding the importance of such knowledge. Methods Eligibility Criteria : Randomized controlled trials (RCTs), case-control, and cohort studies including medical doctors except surgeons for any intervention, reporting the proportion of variance in patients’ outcomes owing to the doctors (random effects), or the fixed effects of grading doctors by outcomes, after multivariate adjustment. Exclusions: studies of <15 doctors or solely reporting doctors’ effects for known variables. Sources Medline, Embase, PsycINFO, inception to June 2020. Manual search for papers referring/referred to by resulting studies. Risk of Bias Using Newcastle–Ottawa scale. Results Despite all medical interventions bar surgery being eligible, only thirty cohort papers were found, covering 36,239 doctors, with 10 specialties, 21 interventions, 60 outcomes (17 unique). Studies reported doctors’ effects by grading doctors from best to worst, or by diversely calculating the doctor-attributed percentage of patients’ outcome variation, ie the intra-class correlation coefficient (ICC). Sixteen studies presented fixed effects, 18 random effects, and 3 another approach. No RCTs found. Thirteen studies reported exceptionally good and/or poor performers with confidence intervals wholly outside the average performance. ICC range 0 to 33%, mean 3.9%. Highly diverse reporting, meta-analysis therefore not applicable. Conclusion Doctors, on their own, can affect patients’ physical health for many interventions and outcomes. Effects range from negligible to substantial, even after accounting for all known variables. Many published cohorts may reveal valuable information by reanalyzing their data for doctors’ effects. Positive and negative doctor outliers appear regularly. Therefore, it can matter which doctor is chosen.