Objectives Clozapine levels may be a more useful predictor of therapeutic response than the dose, given the variability in clozapine metabolism between individuals. We therefore systematically reviewed and meta‐analysed the impact of clozapine levels on response and/or relapse to provide guidance on optimal clozapine levels. Methods We systematically searched PubMed, PsycInfo and Embase for studies exploring clozapine levels and response and/or relapse. Our primary meta‐analysis was rates of response above and below clozapine level thresholds of 350 ng/ml and 600 ng/ml. Secondary analyses were undertaken of mean clozapine levels, dose and concentration/dose (C/D) ratio and response and/or relapse. A meta‐regression by study duration was conducted. Results Twenty studies met inclusion criteria. Clozapine levels above 350 ng/ml were associated with statistically significantly higher rates of response (OR 2.27 95% CI 1.40–3.67, p < 0.001), but not above 600 ng/ml (OR 1.40 95% CI 0.85–2.31, p = 0.19). Higher mean clozapine levels were associated with better rates of response (SMD 0.24, 95% CI 0.00–0.49, p = 0.05), and lower rates of relapse (SMD −0.72, 95% CI −1.26 to −0.19, p = 0.008). By contrast, neither clozapine dose nor C/D ratio was associated with differing rates of response. Similarly, study duration did not affect outcome. Conclusions Our findings are in keeping with current guidelines that recommend targeting clozapine levels above 350 ng/ml before augmentation is considered. As some clozapine associated ADRs are dose dependent, levels above 600 ng/ml may have an unfavourable risk‐benefit ratio.

Objective: Antibiotics can be prescribed as prophylaxis against surgical site infection (SSI) in dermatological surgery. In accordance with antibiotic stewardship, clinical evidence should inform judicious antibiotic prescribing. This review aimed to identify patient and procedure related risk factors for SSI following minor dermatological surgery. Data sources: MEDLINE, CINAHL, Informit and Scopus databases were searched for relevant literature on patient populations receiving minor surgery, where risk factors for SSI were explicitly stated. Study Selection: Studies involving major dermatological surgery were excluded. The preliminary search yielded 820 studies after removing duplicates. 210 abstracts were screened, and 42 full texts were assessed for eligibility. A total of 13 papers were included. Studies were appraised using the Newcastle-Ottawa Quality Assessment Scale. Data Extraction: An electronic data collection tool was constructed to extract information from the eligible studies, and distributed to participating authors. Data synthesis: Risk factors identified included age, sex, diabetes mellitus, chronic obstructive pulmonary disease (COPD), anti-hypertensive and corticosteroid use, smoking, surgery on the lower or upper extremities, excision of non-melanocytic skin cancers (NMSC), large skin excisions and complex surgical techniques. A maximum of two studies agreed on any one risk factor and there were insufficient studies for meta-analysis. Conclusions: Re-excision of skin cancer, below knee excisions and intra-operative haemorrhagic complications were predictive for infection in more than one study. More highquality studies are required to accurately identify risk factors so they can be reliably used in clinical guidelines. the Infectious Diseases Society of America and the Society for Healthcare Epidemiology of America is that antibiotic therapy should be based on patient specific factors, 3 hence an awareness of patients who are at higher risk of SSI is necessary to encourage more judicious antibiotic prescribing. To accurately define patient groups predisposed to developing a SSI, a comprehensive understanding of patient, procedural and physician related risk factors is necessary. Extensive clinical studies have investigated these risk factors in small to large cohorts, however to our knowledge few studies have presented a large systematic review of all possible risk factors which contribute to an individual's overall risk of infection. This review aims to systematically appraise the current evidence of risk factors for SSI in minor dermatological surgery, and identify where further research may be required. Methods Protocol/registration The systematic review was registered in the PROSPERO international prospective register of systematic reviews (ID CRD42016045830). Eligibility criteria Two eligibility criteria were applied in this review. The first was based on a population, intervention, comparison and outcome (PICO) strategy (Table 1). Eligible papers examined