David Bock

A review and discussion of prospective statistical surveillance in public health

A review of methods suggested in the literature for sequential detection of changes in public health surveillance data is presented. Many researchers have noted the need for prospective methods. In recent years there has been an increased interest in both the statistical and the epidemiological literature concerning this type of problem. However, most of the vast literature in public health monitoring deals with retrospective methods, especially spatial methods. Evaluations with respect to the statistical properties of interest for prospective surveillance are rare. The special aspects of prospective statistical surveillance and different ways of evaluating such methods are described. Attention is given to methods that include only the time domain as well as methods for detection where observations have a spatial structure. In the case of surveillance of a change in a Poisson process the likelihood ratio method and the Shiryaev-Roberts method are derived. Copyright 2003 Royal Statistical Society.

Modeling influenza incidence for the purpose of on-line monitoring.

We describe and discuss statistical models of Swedish influenza data, with special focus on aspects which are important in on-line monitoring. Earlier suggested statistical models are reviewed and the possibility of using them to describe the variation in influenza-like illness (ILI) and laboratory diagnoses (LDI) is discussed. Exponential functions were found to work better than earlier suggested models for describing the influenza incidence. However, the parameters of the estimated functions varied considerably between years. For monitoring purposes we need models which focus on stable indicators of the change at the outbreak and at the peak. For outbreak detection we focus on ILI data. Instead of a parametric estimate of the baseline (which could be very uncertain), we suggest a model utilizing the monotonicity property of a rise in the incidence. For ILI data at the outbreak, Poisson distributions can be used as a first approximation. To confirm that the peak has occurred and the decline has started, we focus on LDI data. A Gaussian distribution is a reasonable approximation near the peak. In view of the variability of the shape of the peak, we suggest that a detection system use the monotonicity properties of a peak.

Some statistical aspects of methods for detection of turning points in business cycles

Abstract Methods for online turning point detection in business cycles are discussed. The statistical properties of three likelihood-based methods are compared. One is based on a Hidden Markov Model, another includes a non-parametric estimation procedure and the third combines features of the other two. The methods are illustrated by monitoring a period of the Swedish industrial production. Evaluation measures that reflect timeliness are used. The effects of smoothing, seasonal variation, autoregression and multivariate issues on methods for timely detection are discussed.

Laparoscopic Lavage for Perforated Diverticulitis With Purulent Peritonitis: A Randomized Trial

Context Patients who have perforated diverticulitis with purulent peritonitis are frequently managed surgically with open colon resection, often together with formation of a stoma. Laparoscopic lavage has been proposed as an alternative surgical approach that might involve less morbidity, including a decreased need for additional operations. Contribution This randomized trial of patients who have perforated diverticulitis with purulent peritonitis found that laparoscopic lavage resulted in a decreased need for reoperations compared with open colon resection. Implication Laparoscopic lavage may be an option for the management of perforated diverticulitis with purulent peritonitis. Diverticulosis of the colon is a common condition in Western countries. The incidence increases with age to reach 34% to 56% of persons older than 70 years (1, 2). In the presence of diverticulosis, 15% to 25% also develop diverticulitis. This can be divided into uncomplicated and complicated disease in which complicated diverticulitis may require surgical intervention (35). Complicated diverticulitis is mostly classified according to the Hinchey grading system (grades I to IV) (6). In Hinchey grades III and IV, diverticular perforation into the abdominal cavity has resulted in purulent or fecal peritonitis, respectively. These conditions require emergency surgical intervention and are associated with high morbidity (25% to 75%) and mortality (2% to 30%) (710). Historically, the Hartmann procedure has been most commonly performed, which includes colon resection and colostomy; another option is resection of the affected part of the colon with primary anastomosis with or without diverting ileostomy (9, 11, 12). The strategy in both cases is to reverse the stoma in a second surgery, with subsequent risk for morbidity and mortality (13). Although stoma reversal is a scheduled surgical procedure, it must be considered as a consequence of the primary procedure and due to perforated diverticulitis. The other option is to avoid further surgery, which will leave the patient with a permanent stoma. Recent literature suggests that perforated diverticulitis with purulent peritonitis could be treated with a less invasive approach and reduce the risk for subsequent procedures. On the basis of prospective data, it was suggested in 2008 (14) that Hinchey grade III perforated diverticulitis could be managed by laparoscopic lavage alone, with reduced risk for morbidity and mortality. The potential benefits of laparoscopic lavage are suggested by case series or retrospective studies and 1 prospective study (15), but they are not substantiated in recently published results from 2 randomized trials (16, 17). In addition, there is 1 ongoing randomized trial (18). We previously published the protocol and short-term results of the present trial (19, 20). The hypothesis in this trial was that laparoscopic lavage as emergency treatment of perforated diverticulitis with purulent peritonitis could be a definitive treatment and would lead to fewer patients in need of further surgeries. The primary objective of this trial was to compare laparoscopic lavage and the Hartmann procedure with regard to the percentage of patients with 1 or more reoperations within 12 months. Secondary objectives included analysis of mortality, adverse events, length of hospital stay, and health-related quality of life. Methods Study Design This prospective, open-label, randomized, controlled trial compared laparoscopic lavage and the Hartmann procedure. Nine departments of surgery in Sweden and Denmark included patients from February 2010 until February 2014. The trial was approved by the Board of Ethical Approval in Gothenburg, Sweden (registration number 378-09) and the Danish ethical committee (protocol H-4-2009-088). A detailed description of the protocol has previously been published (19) and is available at www.ssorg.net. Patients We included patients who had suspected acute perforated diverticulitis and imaging showing intra-abdominal free air or fluid and were candidates for surgery (as judged by the surgeon). Those unfit for surgery or participating in conflicting trials were not included. Patients gave written informed consent. Those with other diagnoses, such as colorectal cancer found in the resected specimen or diagnosed at a later colon examination (which was part of the trial protocol), or those who withdrew their consent after being randomly assigned were not included in the per-protocol analysis of the primary outcome. A screening log was held, with monthly review of all patients discharged with a diagnosis of diverticulitis. Those who could be included but were not were recorded retrospectively. Randomization The on-call surgeon enrolled the participants in accordance to the inclusion criteria. The protocol did not require the surgeon to specialize in colorectal surgery. Diagnostic laparoscopy was performed. If Hinchey grade III perforated diverticulitis was found, patients were randomly assigned to either laparoscopic lavage (intervention) or the Hartmann procedure (control). Randomization was stratified by hospital in blocks of 10 with a 1:1 allocation ratio. The sequence was computer-generated by an independent statistician. Allocation was concealed to the staff by sequentially numbered, opaque, sealed envelopes. The circulating nurse in the operating room opened the envelope after the surgeon decided to randomly assign the patient to a group. Procedures In the intervention group, laparoscopic lavage was performed with saline at body temperature, 3 L or more, until clear fluid was returned. In the control group, colon resection and colostomy with open technique was performed (the Hartmann procedure). Both groups received a passive drain in the pelvis, which was left in place for at least 24 hours. The postoperative care was conducted according to local guidelines. All specimens removed during surgery in the Hartmann group had pathologic analysis. If a diagnosis other than diverticulitis was found, the patient was not included in the secondary analysis. Data were collected prospectively by health care professionals using clinical record forms at baseline, during the operation, for the postoperative period until discharge from the hospital, and at each follow-up (6 to 12 weeks, 6 months, and 12 months). Assessment at follow-ups included clinical examination, listing of adverse events, and readmissions or reoperations. Colon examination (colonoscopy or computed tomography colonography) was to be performed within 12 months to exclude other possible diagnoses. All patients were asked to complete the EuroQol 5-dimensional questionnaire (EuroQol-5D) containing generic (nonspecific) instruments at discharge and both the EuroQol-5D and Short Form-36 Health Survey (SF-36) (2123) at 6 and 12 months. The validated Swedish and Danish translations of the instruments were used (2426). EuroQol-5D allows for comparisons between patients with different diseases and representative normative populations and includes 5 dimensions of health (mobility, self-care, usual activities, pain or comfort, and anxiety or depression). The answering categories were no problems, low levels of problems, and severe problems. It also assesses global health from worst imaginable health state (score of 0) to best imaginable health state (score of 100) using a visual analogue scale. The questionnaire reflects the respondents situation at the day of completion. The SF-36 is a generic instrument consisting of 8 sections and can be used to evaluate a patients health status with a 14-day recall period. It was summarized into physical and mental component summary scores (27). Outcomes The primary outcome was the percentage of patients with 1 or more reoperations within 12 months. We defined the term 12-month follow-up used in the protocol as 12 months plus 30 days for practical reasons because all follow-up visits were not performed at exactly 12 months. Secondary outcomes were number of reoperations, hospital readmissions, total length of hospital stay during 12-month follow-up, postoperative adverse events, incisional hernia, bowel obstruction, mortality, persisting stoma at 12 months, and quality of life. Data on adverse events were collected prospectively in the clinical record forms, and before analysis, they were classified retrospectively according to ClavienDindo (28). This classification is based on the type of treatment required for the adverse event. Before classification, a decision was made to combine Hinchey grade I and II cases to reduce the risk for misclassification. Percutaneous drainage without general anesthesia was not registered as a reoperation but as an adverse event. Statistical Analysis In a retrospective study, 40% of patients who had the Hartmann procedure because of perforated diverticulitis had another operation at least once within 12 months after the index procedure (7). To detect a 75% reduction in the relative risk for the primary end point, 32 evaluable patients per group were required, assuming an annual incidence of 40% in the control group with 80% power using a 2-sided chi-square test at the 5% significance level. A statistical analysis plan was created before the analysis. The main analysis population consisted of all randomly assigned patients. In addition, an analysis of a per-protocol population was performed. The primary and secondary outcomes were analyzed with a generalized linear model using robust variance estimation and a log-link function with group as the factor, site as the covariate, and log (time in study) as the offset (29). For the primary outcome, we used a Poisson distribution because the model failed to converge for a binomial distribution (30). For the secondary outcomes, we used a negative binomial distribution. Length of hospital stay (total number of days during 12-month follow-up) had a right-skewed distribution and was analyzed by a linear mode

Extralevator Abdominoperineal Excision for Low Rectal Cancer--Extensive Surgery to Be Used With Discretion Based on 3-Year Local Recurrence Results: A Registry-based, Observational National Cohort Study.

Objectives:The aim of this prospective registry-based population study was to investigate the efficacy of extralevator abdominoperineal excision (ELAPE) regarding local recurrence rates within 3 years after surgery. Background:Local recurrence of rectal cancer is more common after abdominoperineal excision (APE) than after anterior resection. Extralevator abdominoperineal excision was introduced to address this problem. No large-scale studies with long-term oncological outcomes have been published. Methods:All Swedish patients operated on with an APE and registered in the Swedish ColoRectal Cancer Registry 2007 to 2009 were included (n = 1397) and analyzed with emphasis on the perineal part of the operation. Local recurrence at 3 years was collected from the registry. Results:The local recurrence rates at 3 years [median follow-up, 3.43 years (APE, 3.37 years; ELAPE, 3.41 years; not stated: 3.43 years)] were significantly higher for ELAPE compared with APE (relative risk, 4.91). Perioperative perforation was also associated with an increased risk of local recurrence (relative risk, 3.62). There was no difference in 3-year overall survival between APE and ELAPE. In the subgroup of patients with very low tumors (⩽4 cm from the anal verge), no significant difference in the local recurrence rate could be observed. Conclusions:Extralevator abdominoperineal excision results in a significantly increased 3-year local recurrence rate as compared with standard APE. Intraoperative perforation seems to be an important risk factor for local recurrence. In addition to significantly increased 3-year local recurrence rates, the significantly increased incidence of wound complications leads to the conclusion that ELAPE should only be considered in selected patients at risk of intraoperative perforation.

Aspects on the control of false alarms in statistical surveillance and the impact on the return of financial decision systems

Abstract In systems for online detection of regime shifts, a process is continually observed. Based on the data available an alarm is given when there is enough evidence of a change. There is a risk of a false alarm and here two different ways of controlling the false alarms are compared: a fixed average run length until the first false alarm and a fixed probability of any false alarm (fixed size). The two approaches are evaluated in terms of the timeliness of alarms. A system with a fixed size is found to have a drawback: the ability to detect a change deteriorates with the time of the change. Consequently, the probability of successful detection will tend to zero and the expected delay of a motivated alarm tends to infinity. This drawback is present even when the size is set to be very large (close to one). Utility measures expressing the costs for a false or a too late alarm are used in the comparison. How the choice of the best approach can be guided by the parameters of the process and the different costs of alarms is demonstrated. The technique is illustrated by financial transactions of the Hang Seng Index.

Early Closure of a Temporary Ileostomy in Patients With Rectal Cancer: A Multicenter Randomized Controlled Trial.

Objective: The objective was to study morbidity and mortality associated with early closure (8–13 days) of a temporary stoma compared with standard procedure (closure after > 12 weeks) after rectal resection for cancer. Background: A temporary ileostomy may reduce the risk of pelvic sepsis after anastomotic dehiscence. However, the temporary ileostomy is afflicted with complications and requires a second surgical procedure (closure) with its own complications. Early closure of the temporary ileostomy could reduce complications for rectal cancer patients. Methods: Early closure (8–13 days after stoma creation) of a temporary ileostomy was compared with late closure (>12 weeks) in a multicenter randomized controlled trial, EASY (www.clinicaltrials.gov, NCT01287637) including patients undergoing rectal resection for cancer. Patients with a temporary ileostomy without signs of postoperative complications were randomized to closure at 8 to 13 days or late closure (>12 weeks after index surgery). Clinical data were collected up to 12 months. Complications were registered according to the Clavien-Dindo Classification of Surgical Complications, and Comprehensive Complication Index was calculated. Results: The trial included 127 patients in eight Danish and Swedish surgical departments, and 112 patients were available for analysis. The mean number of complications after index surgery up to 12 months follow up was significantly lower in the intervention group (1.2) compared with the control group (2.9), P < 0.0001. Conclusions: It is safe to close a temporary ileostomy 8 to 13 days after rectal resection and anastomosis for rectal cancer in selected patients without clinical or radiological signs of anastomotic leakage.

Health economic analysis of laparoscopic lavage versus Hartmann's procedure for diverticulitis in the randomized DILALA trial

Open surgery with resection and colostomy (Hartmanns procedure) has been the standard treatment for perforated diverticulitis with purulent peritonitis. In recent years laparoscopic lavage has emerged as an alternative, with potential benefits for patients with purulent peritonitis, Hinchey grade III. The aim of this study was to compare laparoscopic lavage and Hartmanns procedure with health economic evaluation within the framework of the DILALA (DIverticulitis – LAparoscopic LAvage versus resection (Hartmanns procedure) for acute diverticulitis with peritonitis) trial.

Is preoperative physical activity related to post-surgery recovery? A cohort study of patients with breast cancer

Objective The aim of our study is to assess the association between preoperative level of activity and recovery after breast cancer surgery measured as hospital stay, length of sick leave and self-assessed physical and mental recovery. Design A prospective cohort study. Setting Patients included were those scheduled to undergo breast cancer surgery, between February and November 2013, at two participating hospitals in the Western Region of Sweden. Participants Patients planned for breast cancer surgery filled out a questionnaire before, as well as at 3 and 6 weeks after the operation. The preoperative level of activity was self-assessed and categorised into four categories by the participants using the 4-level Saltin-Grimby Physical Activity Level Scale (SGPALS). Main outcome measure Our main outcome was postoperative recovery measured as length of sick leave, in-hospital stay and self-assessed physical and mental recovery. Results 220 patients were included. Preoperatively, 14% (31/220) of participants assessed themselves to be physically inactive, 61% (135/220) to exert some light physical activity (PA) and 20% (43/220) to be more active (level 3+4). Patients operated with mastectomy versus partial mastectomy and axillary lymph node dissection versus sentinel node biopsy were less likely to have a short hospital stay, relative risk (RR) 0.88 (0.78 to 1.00) and 0.82 (0.70 to 0.96). More active participants (level 3 or 4) had an 85% increased chance of feeling physically recovered at 3 weeks after the operation, RR 1.85 (1.20 to 2.85). No difference was seen after 6 weeks. Conclusions The above study shows that a higher preoperative level of PA is associated with a faster physical recovery as reported by the patients 3 weeks post breast cancer surgery. After 6 weeks, most patients felt physically recovered, diminishing the association above. No difference was seen in length of sick leave or self-assessed mental recovery between inactive or more active patients.

Changes in safety climate and teamwork in the operating room after implementation of a revised WHO checklist: a prospective interventional study

BackgroundInter-professional teamwork in the operating room is important for patient safety. The World Health Organization (WHO) checklist was introduced to improve intraoperative teamwork. The aim of this study was to evaluate the safety climate in a Swedish operating room setting before and after an intervention, using a revised version of the WHO checklist to improve teamwork.MethodsThis study is a single center prospective interventional study. Participants were personnel working in operating room teams including surgeons, anesthesiologists, scrub nurses, nurse anaesthetists and nurse assistants. The study started with pre-interventional observations of the WHO checklist use followed by education on safety climate, the WHO checklist, and non-technical skills in the operating room. Thereafter a revised version of the WHO checklist was introduced. Post-interventional observations regarding the performance of the WHO checklist were carried out. The Safety Attitude Questionnaire was used to assess safety climate at baseline and post-intervention.ResultsAt baseline we discovered a need for improved teamwork and communication. The participants considered teamwork to be important for patient safety, but had different perceptions of good teamwork between professions. The intervention, a revised version of the WHO checklist, did not affect teamwork climate. Adherence to the revision of the checklist was insufficient, dominated by a lack of structure.ConclusionsThere was no significant change in teamwork climate by use of the revised WHO checklist, which may be due to insufficient implementation, as a lack of adherence to the WHO checklist was detected. We found deficiencies in teamwork and communication. Further studies exploring how to improve safety climate are needed.Trial registrationNCT02329691.