Background Acute kidney injury (AKI) is a serious global public health problem. We aimed to quantify the risk of AKI associated with estimated glomerular filtration rate (eGFR), albuminuria (albumin-creatinine ratio [ACR]), age, sex, and race (African American and Caucasian). Study Design Collaborative meta-analysis. Setting & Population 8 general population cohorts (1,285,049 participants) and 5 chronic kidney disease (CKD) cohorts (79,519 participants). Selection Criteria for Studies Available eGFR, ACR, and ≥50 AKI events. Predictors Age, sex, race, eGFR, urine ACR, and interactions. Outcome Hospitalized with or for AKI, using Cox proportional hazards models to estimate HRs of AKI and random effects meta-analysis to pool results. Results 16,480 (1.3%) general population cohort participants had AKI over a mean follow-up of 4 years; 2,087 (2.6%) CKD participants had AKI over mean follow-up of 1 year. Lower eGFR and higher ACR were strongly associated with AKI. Compared with eGFR 80 ml/min/1.73 m2, the adjusted HR of AKI at eGFR 45 ml/min/1.73 m2 was 3.35 (95% CI, 2.75–4.07). Compared with ACR 5 mg/g, the risk of AKI at ACR 300 mg/g was 2.73 (95% CI, 2.18–3.43). Older age was associated with higher risk of AKI, but this effect was attenuated in lower eGFR or higher ACR. Male sex was associated with higher risk of AKI, with a slight attenuation in lower eGFR but not in higher ACR. African Americans had higher AKI risk at higher levels of eGFR and most levels of ACR. Limitations Only 2 general population cohorts could contribute to analyses by race; AKI identified by diagnostic code. Conclusions Reduced eGFR and increased ACR are consistent, strong risk factors for AKI whereas the associations of AKI with age, sex, and race may be weaker in more advanced stages of CKD.

Background Surgical site infection (SSI) affects up to 20% of people with a primary closed wound after surgery. Wound dressings may reduce SSI. Objective To assess the feasibility of a multicentre randomised controlled trial (RCT) to evaluate the effectiveness and cost-effectiveness of dressing types or no dressing to reduce SSI in primary surgical wounds. Design Phase A – semistructured interviews, outcome measure development, practice survey, literature reviews and value-of-information analysis. Phase B – pilot RCT with qualitative research and questionnaire validation. Patients and the public were involved. Setting Usual NHS care. Participants Patients undergoing elective/non-elective abdominal surgery, including caesarean section. Interventions Phase A – none. Phase B – simple dressing, glue-as-a-dressing (tissue adhesive) or ‘no dressing’. Main outcome measures Phase A – pilot RCT design; SSI, patient experience and wound management questionnaires; dressing practices; and value-of-information of a RCT. Phase B – participants screened, proportions consented/randomised; acceptability of interventions; adherence; retention; validity and reliability of SSI measure; and cost drivers. Data sources Phase A – interviews with patients and health-care professionals (HCPs), narrative data from published RCTs and data about dressing practices. Phase B – participants and HCPs in five hospitals. Results Phase A – we interviewed 102 participants. HCPs interpreted ‘dressing’ variably and reported using available products. HCPs suggested practical/clinical reasons for dressing use, acknowledged the weak evidence base and felt that a RCT including a ‘no dressing’ group was acceptable. A survey showed that 68% of 1769 wounds (727 participants) had simple dressings and 27% had glue-as-a-dressing. Dressings were used similarly in elective and non-elective surgery. The SSI questionnaire was developed from a content analysis of existing SSI tools and interviews, yielding 19 domains and 16 items. A main RCT would be valuable to the NHS at a willingness to pay of £20,000 per quality-adjusted life-year. Phase B – from 4 March 2016 to 30 November 2016, we approached 862 patients for the pilot RCT; 81.1% were eligible, 59.4% consented and 394 were randomised (simple, n = 133; glue, n = 129; no dressing, n = 132); non-adherence was 3 out of 133, 8 out of 129 and 20 out of 132, respectively. SSI occurred in 51 out of 281 participants. We interviewed 55 participants. All dressing strategies were acceptable to stakeholders, with no indication that adherence was problematic. Adherence aids and patients’ understanding of their allocated dressing appeared to be key. The SSI questionnaire response rate overall was 67.2%. Items in the SSI questionnaire fitted a single scale, which had good reliability (test–retest and Cronbach’s alpha of > 0.7) and diagnostic accuracy (c-statistic = 0.906). The key cost drivers were hospital appointments, dressings and redressings, use of new medicines and primary care appointments. Limitations Multiple activities, often in parallel, were challenging to co-ordinate. An amendment took 4 months, restricting recruitment to the pilot RCT. Only 67% of participants completed the SSI questionnaire. We could not implement photography in theatres. Conclusions A main RCT of dressing strategies is feasible and would be valuable to the NHS. The SSI questionnaire is sufficiently accurate to be used as the primary outcome. A main trial with three groups (as in the pilot) would be valuable to the NHS, using a primary outcome of SSI at discharge and patient-reported SSI symptoms at 4–8 weeks. Trial registration Phase A – Current Controlled Trials ISRCTN06792113; Phase B – Current Controlled Trials ISRCTN49328913. Funding This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 23, No. 39. See the NIHR Journals Library website for further project information. Funding was also provided by the Medical Research Council ConDuCT-II Hub (reference number MR/K025643/1).

Background Accurate assessment of surgical‐site infection (SSI) is crucial for surveillance and research. Self‐reporting patient measures are needed because current SSI tools are limited for assessing patients after leaving hospital. The Bluebelle Wound Healing Questionnaire (WHQ) was developed for patient or observer completion; this study tested its acceptability, scale structure, reliability and validity in patients with closed primary wounds after abdominal surgery. Methods Patients completed the WHQ (self‐assessment) within 30 days after leaving hospital and returned it by post. Healthcare professionals completed the WHQ (observer assessment) by telephone or face‐to‐face. Questionnaire response rates and patient acceptability were assessed. Factor analysis and Cronbach's α examined scale structure and internal consistency. Test–retest and self‐ versus observer reliability assessments were performed. Sensitivity and specificity for SSI discrimination against a face‐to‐face reference diagnosis (using Centers for Disease Control and Prevention criteria) were examined. Results Some 561 of 792 self‐assessments (70·8 per cent) and 597 of 791 observer assessments (75·5 per cent) were completed, with few missing data or problems reported. Data supported a single‐scale structure with strong internal consistency (α greater than 0·8). Reliability between test–retest and self‐ versus observer assessments was good (κ 0·6 or above for the majority of items). Sensitivity and specificity for SSI discrimination was high (area under the receiver operating characteristic (ROC) curve 0·91). Conclusion The Bluebelle WHQ is acceptable, reliable and valid with a single‐scale structure for postdischarge patient or observer assessment of SSI in closed primary wounds.

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BackgroundSurgical site infections (SSIs) are common, occurring in up to 25% of > 4 million operations performed in England each year. Previous trials of the effect of wound dressings on the risk of developing a SSI are of poor quality and underpowered.Methods/DesignThis study is a feasibility and pilot trial to examine the feasibility of a full trial that will compare simple dressings, no dressing and tissue-glue as a dressing. It is examining the overall acceptability of trial participation, identifying opportunities for refinement, testing the feasibility of and validating new outcome tools to assess SSI, wound management issues and patients’ wound symptom experiences. It is also exploring methods for avoiding performance bias and blinding outcome assessors by testing the feasibility of collecting wound photographs taken in theatre immediately after wound closure and, at 4–8 weeks after surgery, taken by participants themselves or their carers. Finally, it is identifying the main cost drivers for an economic evaluation of dressing types. Integrated qualitative research is exploring acceptability and reasons for non-adherence to allocation. Adults undergoing primary elective or unplanned abdominal general surgery or Caesarean section are eligible. The main exclusion criteria are abdominal or other major surgery less than three months before the index operation or contraindication to dressing allocation. The trial is scheduled to recruit for nine months. The findings will be used to inform the design of a main trial.DiscussionThis pilot trial is the first pragmatic study to randomise participants to no dressing or tissue-glue as a dressing versus a simple dressing. Early evidence from the ongoing pilot shows that recruitment is proceeding well and that the interventions are acceptable to participants. Combined with the qualitative findings, the findings will inform whether a main, large trial is feasible and, if so, how it should be designed.Trial registration ISRCTN49328913. Registered on 20 October 2015.Electronic supplementary materialThe online version of this article (doi:10.1186/s13063-017-2102-5) contains supplementary material, which is available to authorized users.

Background Increased total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), and decreased high-density lipoprotein cholesterol (HDL-C) concentrations, are established risk factors for cardiovascular morbidity and mortality; but their impact on the risk of advanced chronic kidney disease (CKD) is unclear. This study evaluates the association between the different lipid profiles and the onset of advanced CKD using a general population sample. Methods This observational study used records of 911,360 individuals from the English Clinical Practice Research Datalink (from 2000 to 2014), linked to coded hospital discharges and mortality registrations. Cox models were used to examine the independent association between the equal quarters of TC, TG, LDL-C, and HDL-C and the risk of advanced CKD, after adjustment for sex and age, and potential effect mediators. Results During a median follow-up of 7.5 years, 11,825 individuals developed CKD stages 4–5. After adjustment for sex and age, the hazard ratios (HRs) and confidence intervals (CIs) for CKD stages 4–5 comparing the 4th vs. 1st quarters of TG and 1st vs. 4th quarters of HDL-C were 2.69 (95% CI, 2.49–2.90) and 2.61 (95% CI, 2.42–2.80), respectively. Additional adjustment for potential effect mediators reduced the HRs to 1.28 (95% CI, 1.15–1.43), and 1.27 (95% CI, 1.14–1.41), respectively. There was no evidence of fully adjusted associations with CKD stages 4–5 for levels of either TC or LDL-C. Conclusions Elevated TG and reduced HDL-C levels are independently associated with the onset of advanced CKD. Future studies, such as in basic science and randomized trials, are needed to understand whether associations between TG and HDL-C and the development of CKD are causal.

BackgroundDesigning RCTs in surgery requires consideration of existing evidence, stakeholders' views and emerging interventions, to ensure that research questions are relevant to patients, surgeons and the health service. When there is uncertainty about RCT design, feasibility work is recommended. This study aimed to assess how feasibility work could inform the design of a future pilot study and RCT (Bluebelle, HTA ‐ 12/200/04).MethodsThis was a prospective survey of dressings used to cover abdominal wounds. Surgical trainees from 25 hospitals were invited to participate. Information on patient risk factors, operation type and type of wound dressings used was recorded for elective and unplanned abdominal procedures over a 2‐week interval. The types of dressing used were summarized, and associations with operation type and patient risk factors explored.ResultsTwenty hospitals participated, providing data from 727 patients (1794 wounds). Wounds were predominantly covered with basic dressings (1203 of 1769, 68·0 per cent) and tissue adhesive was used in 27·4 per cent (485 of 1769); dressing type was missing for 25 wounds. Just 3·6 per cent of wounds (63 of 1769) did not have a dressing applied at the end of the procedure. There was no evidence of an association between type of dressing used and patient risk factors, type of operation, or elective and unscheduled surgery.ConclusionBased on the findings from this large study of current practice, the pilot study design has evolved. The inclusion criteria have expanded to encompass patients undergoing unscheduled surgery, and tissue adhesive as a dressing will be evaluated as an additional intervention group. Collaborative methods are recommended to inform the design of RCTs in surgery, helping to ensure they are relevant to current practice.

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