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Ascertainment of gastroschisis using the ICD-9-CM surgical procedure code.

OBJECTIVE: To determine the effectiveness of using the ICD-9-CM procedure code 54.71 for case ascertainment of gastroschisis. METHODS: Using procedure code 54.71, we queried a statewide hospital discharge database to identify all cases coded as undergoing surgical repair of gastroschisis. Each retrieved case was verified as having gastroschisis by review of the hospital record. All gastroschisis cases were then matched to the Florida Birth Defect Registry (FBDR) dataset. This registry uses a passive system of multiple data sources and employs the ICD-9-CM diagnostic code 756.79 to identify gastroschisis and other abdominal wall defects. RESULTS: Of 93 cases identified by using code 54.71, 92 were confirmed by record review to have gastroschisis. The FBDR identified 87 of the 92 cases (95%). The FBDR missed three of the remaining five cases because of linkage difficulties between inconsistent data elements in the respective data files. The other two cases were not identified by the FBDR because the source database (AHCA discharge) truncates the entry of ICD-9-CM diagnostic codes when more than 10 of them are listed in the medical record. CONCLUSIONS: Use of the surgical procedure code was demonstrated to be superior to the diagnostic code as a method for identification of gastroschisis cases. The same approach may be useful in the detection of malformations other than gastroschisis.

Adult↗

Large-scale in-vivo Caucasian facial soft tissue thickness database for craniofacial reconstruction.

A large-scale study of facial soft tissue depths of Caucasian adults was conducted. Over a 2-years period, 967 Caucasian subjects of both sexes, varying age and varying body mass index (BMI) were studied. A user-friendly and mobile ultrasound-based system was used to measure, in about 20min per subject, the soft tissue thickness at 52 facial landmarks including most of the landmarks used in previous studies. This system was previously validated on repeatability and accuracy [S. De Greef, P. Claes, W. Mollemans, M. Loubele, D. Vandermeulen, P. Suetens, G. Willems, Semi-automated ultrasound facial soft tissue depth registration: method and validation. J. Forensic Sci. 50 (2005)]. The data of 510 women and 457 men were analyzed in order to update facial soft tissue depth charts of the contemporary Caucasian adult. Tables with the average thickness values for each landmark as well as the standard deviation and range, tabulated according to gender, age and BMI are reported. In addition, for each landmark and for both sexes separately, a multiple linear regression of thickness versus age and BMI is calculated. The lateral asymmetry of the face was analysed on an initial subset of 588 subjects showing negligible differences and thus warranting the unilateral measurements of the remaining subjects. The new dataset was statistically compared to three datasets for the Caucasian adults: the traditional datasets of Rhine and Moore [J.S. Rhine, C.E. Moore, Tables of facial tissue thickness of American Caucasoids in forensic anthropology. Maxwell Museum Technical series 1 (1984)] and Helmer [R. Helmer, Schädelidentifizierung durch elektronische bildmischung, Kriminalistik Verlag GmbH, Heidelberg, 1984] together with the most recent in vivo study by Manhein et al. [M.H. Manhein, G.A. Listi, R.E. Barsley, R. Musselman, N.E. Barrow, D.H. Ubelbaker, In vivo facial tissue depth measurements for children and adults. J. Forensic Sci. 45 (2000) 48-60]. The large-scale database presented in this paper offers a denser sampling of the facial soft tissue depths of a more representative subset of the actual Caucasian population over the different age and body posture subcategories. This database can be used as an updated chart for manual and computer-based craniofacial approximation and allows more refined analyses of the possible factors affecting facial soft tissue depth.

Adolescent↗

Evidence based medicine in clinical practice: how to advise patients on the influence of age on the outcome of surgical anterior cruciate ligament reconstruction: a review of the literature.

OBJECTIVE: To determine, using a literature search, whether patient age influences the outcome of surgical reconstruction of a torn anterior cruciate ligament. METHODS: Medline (1966 to present) was searched using the PubMed interface, Embase (1974 to present) using the Datastar system, and the Cochrane Library at the Update Software web site. Papers retrieved from the three databases were independently assessed by two reviewers using preliminary inclusion criteria. Reference lists of papers satisfying the preliminary criteria were then scanned and appropriate papers reviewed. Any new papers in turn had their reference lists scanned, this process continuing until no new papers were identified. Final inclusion criteria were then applied to all papers satisfying the preliminary inclusion criteria. RESULTS: The initial search identified 661 papers. Exclusion of duplicates produced 536 unique papers. Medline contained 445, Embase 185, and the Cochrane Library 31. Of the 536, 523 were assessed by abstract and 12 by full text; one paper was not retrieved. Application of the preliminary inclusion criteria produced 33 papers. Their reference lists contained 950 references. Scanning of these added six new papers to the dataset. These six had their reference lists assessed; no new papers were identified. Four of the 39 papers in the completed dataset satisfied the final inclusion criteria. There was wide variation in the total number of subjects in the four studies, ranging from 22 to 203 patients. The total number of different outcome measures was 17; only one measure was used by all four studies. None of the objective outcome measures showed any significant difference between age groups, and the subjective measures, which did show differences, were contradictory. A total of 108 interlibrary loans were requested, by a full time researcher, at a total cost of 432.00 Irish pounds over a 10 week period. CONCLUSIONS: When advising patients on the outcome of anterior cruciate ligament reconstruction, age should not be considered in isolation. In the absence of relevant guidelines, meta-analyses, or systematic reviews, the application of evidence based medicine to clinical practice has significant resource implications.

Adult↗

The impact on family scale revisited: further psychometric data.

This article presents additional psychometric data and a revised scoring procedure for the widely used Impact on Family Scale. The analyses were conducted with three datasets produced by validation studies conducted at the originating institution with populations drawn from the same inner-city communities as the original sample. The instrument has one robust factor representing overall family impact. In addition, there are two subsidiary sets of items (financial impact and sibling impact) of possible interest to future researchers. The correlation of the previously published and new Total Score is .97. Data indicate that the Impact on Family Scale is an easily administered, reliable, and valid measure of a family member's perception of the effect of a child's chronic condition that can be used across diagnostic groups. The Impact on Family Scale fills a gap in the measurement of the psychological and social consequences of chronic disorders in childhood that can be useful in clinical and health services research.

Child↗

Development and evaluation of an automated atlas-based image analysis method for microPET studies of the rat brain.

An automated method for placement of 3D rat brain atlas-derived volumes of interest (VOIs) onto PET studies has been designed and evaluated. VOIs representing major structures of the rat brain were defined on a set of digitized cryosectioned images of the rat brain. For VOI placement, each PET study was registered with a synthetic PET target constructed from the VOI template. Registration was accomplished with an automated algorithm that maximized the mutual information content of the image volumes. The accuracy and precision of this method for VOI placement was determined using datasets from PET studies of the striatal dopamine and hippocampal serotonin systems. Each evaluated PET study could be registered to at least one synthetic PET target without obvious failure. Registration was critically dependent upon the initial position of the PET study relative to the synthetic PET target, but not dependent on the amount of synthetic PET target smoothing. An evaluation algorithm showed that resultant radioactivity concentration measurements of selected brain structures had errors=2% due to misalignment with the corresponding VOI. Further, radioligand binding values calculated from these measurements were found to be more precise than those calculated from measurements obtained with manually drawn regions of interest (ROIs). Overall, evaluation results demonstrated that this atlas-derived VOI method can be used to obtain unbiased measurements of radioactivity concentration from PET studies. Its automated features, and applicability to different radioligands and brain regions, will facilitate quantitative rat brain PET assessment procedures.

Animals↗

Education, gender, and mortality: does schooling have the same effect on mortality for men and women in the US?

In this paper I examine whether the effect of education on mortality for US adults differs by gender. Discrete time logit models were used to analyze a nationally representative dataset (NHANES I) with 12,036 adults who were 25-74-years-old at the baseline survey in 1971-1975, and then re-interviewed three times through 1992. Demographic characteristics, health behaviors and economic status were controlled as potential confounding or mediating factors in the education-mortality relationship. The results showed that education had a comparable effect on mortality for men and women. No statistically significant gender difference was found in all-cause mortality, or mortality by cause of death, among younger persons, and among the elderly. Analysis by marital status, however, suggested that these findings apply only to married men and women. Among the divorced, there was a statistically significant gender difference whereby education had no effect on mortality for men while divorced women evidenced a strong education gradient (seven percent lower odds of dying for each year of schooling). Possible explanations for these patterns are discussed.

Adult↗

Using the STS and multinational cardiac surgical databases to establish risk-adjusted benchmarks for clinical outcomes.

One of the purposes of collecting data on cardiac surgical procedures, at a national level is to enable individual surgeons to improve quality and benchmark their own practice by making more accurate prospective prediction of outcome of each individual patient by using risk stratification based on previous local and national experiences. The past decade has seen a dramatic increase in the development of national cardiac surgical initiatives in many countries around the world. The size and extent of these databases has successfully allowed their use for patient risk stratification and preoperative risk modeling in four main aspects: patient selection and informed consent, coherent analysis of the determinants of patient outcomes, rationalizing unit management, and negotiations with external agencies. Approximately 610 cardiac surgical units presently contribute their patient data, containing pre-operative risk factors, to centralized national registries. There are currently nine different datasets used throughout the world to collect patient information. To harmonize the considerable diversity among these source materials, an International Dataset has been developed by a collaborative process among more than 50 cardiac surgeons around the world. Constructed around the Society of Thoracic Surgeons (STS) data format, the International Dataset brings in key elements from all the other datasets, allowing the sharing of data and cross-analysis, thus greatly expanding the pool of patients, and national sources, from which risk-stratifed outcomes can now be analyzed and unified. Unlike the STS dataset, the International Dataset incorporates EuroSCORE, a simple-to-use, validated patient risk stratification system, which has been rapidly adopted by large numbers of centers around the world for patient risk stratification, outcomes assessment, and improving patient informed consent. There are several benefits to collecting and centralizing national and international data: (1) understanding and defining basic demographics of patients undergoing cardiac surgery; (2) patient risk stratification and risk prediction at both a national and center-by-center level; (3) unit benchmarking, and development of effective nationally oriented and center-oriented quality improvement programs; (4) understanding and rationalizing resource utilization; and (5) use of data to leverage governments and other healthcare providers to affect policy. Cardiac surgical registries will soon attempt to track patients for longer follow-up periods after discharge in order to identify surgery-related deaths for more extended periods of time following surgery, thereby improving the monitoring and prediction of patient outcomes.

Benchmarking↗

Sensitivity analysis and external adjustment for unmeasured confounders in epidemiologic database studies of therapeutics.

BACKGROUND: Large health care utilization databases are frequently used to analyze unintended effects of prescription drugs and biologics. Confounders that require detailed information on clinical parameters, lifestyle, or over-the-counter medications are often not measured in such datasets, causing residual confounding bias. OBJECTIVE: This paper provides a systematic approach to sensitivity analyses to investigate the impact of residual confounding in pharmacoepidemiologic studies that use health care utilization databases. METHODS: Four basic approaches to sensitivity analysis were identified: (1) sensitivity analyses based on an array of informed assumptions; (2) analyses to identify the strength of residual confounding that would be necessary to explain an observed drug-outcome association; (3) external adjustment of a drug-outcome association given additional information on single binary confounders from survey data using algebraic solutions; (4) external adjustment considering the joint distribution of multiple confounders of any distribution from external sources of information using propensity score calibration. CONCLUSION: Sensitivity analyses and external adjustments can improve our understanding of the effects of drugs and biologics in epidemiologic database studies. With the availability of easy-to-apply techniques, sensitivity analyses should be used more frequently, substituting qualitative discussions of residual confounding.

Anti-Inflammatory Agents, Non-Steroidal↗

Evaluation of approaches for terrestrial hazard classification.

Hazard assessment is an essential element in the evaluation of the potential effects of chemical substances on the environment. To date, most work has focused on hazard assessment schemes for the aquatic environment, but in recent years, a number of proposals have been developed for other environmental compartments. Due to limited datasets, the suitability of the toxicity cut-off values in these schemes has not been fully determined and the practicalities associated with using these approaches have not been fully established. This study, which focused on the soil compartment, was performed to examine cut-off values proposed by two terrestrial hazard assessment schemes and establish the availability of data. Data on earthworms indicated that current proposals for toxicity cut-off values are appropriate. However, analysis of IUCLID (International Uniform ChemicaL Information Database) indicates that even for commonly used high production volume chemicals, insufficient data are available to enable classification. Whilst the necessary data may already be available for selected groups of substances (e.g. pesticides and veterinary medicines), a significant experimental testing programme would therefore be required before a terrestrial classification system could be applied widely. Such data may become available in the future as a result of initiatives such as REACH.

Animals↗

Obesity among children attending elementary public schools in São Paulo, Brazil: a case--control study.

OBJECTIVES: To describe obesity among students of public schools in São Paulo and to identify risk factors for this nutritional and physical activity disorder. DESIGN: Case-control study of obese and non-obese schoolchildren to study risk factors for obesity. SETTING: Anthropometric survey including 2519 children attending eight elementary public schools in São Paulo, Brazil. SUBJECTS: Schoolchildren aged 7-10 years, of whom 223 were obese (cases; weight-for-height greater than or equal to two standard deviations (>or=2SD) above the median of the National Center for Health Statistics (NCHS) reference population) and 223 were eutrophic (controls; weight-for-height +/-1SD from NCHS median). MEASUREMENTS: Parents or guardians of the 446 cases and controls were interviewed about the children's eating behaviours and habits. RESULTS: The prevalence of obesity (weight-for-height >or=2SD) in the surveyed population was 10.5%. A logistic regression model fitted to the case-control dataset showed that obesity was positively associated with the following factors: birth weight >or=3500 g (odds ratio (OR) 1.83, 95% confidence interval (CI) 1.21-2.78), child's appetite at meals (OR 3.81, 95% CI 2.49-5.83), watching television for 4 h per day or longer (OR 2.07, 95% CI 1.32-3.24), mother's schooling >4 years (OR 1.85, 95% CI 1.25-2.75) and parents' body mass index >or=30 kg x m(-2) (OR 2.50, 95% CI 1.43-4.37). CONCLUSIONS: The explanatory multivariate model points to preventive measures that would encourage knowledge of the children and their guardians in relation to a balanced diet and a less sedentary lifestyle, such as reducing television viewing. Schoolchildren with a birth weight of 3500 g or more or whose parents are obese should receive special attention in the prevention of obesity.

Anthropometry↗

Computerized outcomes analysis for congenital heart disease.

PURPOSE OF REVIEW: This paper reviews the past year's literature on computerized outcomes analysis for congenital heart disease. RECENT FINDINGS: This review focuses on recent advances in four areas of computerized outcomes analysis for congenital heart disease: nomenclature, database, complexity adjustment, and data verification. A common nomenclature, along with a common core minimal dataset, were adopted by the European Association for Cardio-thoracic Surgery and the Society of Thoracic Surgeons and published in 2000 in the Annals of Thoracic Surgery; the thrust towards the establishment of an international nomenclature is now being developed further by the International Society for Nomenclature of Pediatric and Congenital Heart Disease [http://www.IPCCC.net]. This common nomenclature and common minimum database dataset, created by the International Congenital Heart Surgery Nomenclature and Database Project, are now used by the European Association for Cardio-thoracic Surgery and Society of Thoracic Surgeons since 1998, this nomenclature and database have been used to analyze outcomes of over 40 000 patients. Two major multi-institutional efforts have attempted to measure case complexity: the Risk Adjustment in Congenital Heart Surgery-1 and the Aristotle Complexity Score. Collaborative efforts involving the European Association for Cardio-thoracic Surgery and Society of Thoracic Surgeons are underway to develop mechanisms to verify data completeness and accuracy. SUMMARY: Methods of congenital heart disease outcomes analysis continue to evolve, with continued advances in four areas: nomenclature, database, complexity adjustment, and data verification.

Child↗

Date of origin of the SARS coronavirus strains.

BACKGROUND: A new respiratory infectious epidemic, severe acute respiratory syndrome (SARS), broke out and spread throughout the world. By now the putative pathogen of SARS has been identified as a new coronavirus, a single positive-strand RNA virus. RNA viruses commonly have a high rate of genetic mutation. It is therefore important to know the mutation rate of the SARS coronavirus as it spreads through the population. Moreover, finding a date for the last common ancestor of SARS coronavirus strains would be useful for understanding the circumstances surrounding the emergence of the SARS pandemic and the rate at which SARS coronavirus diverge. METHODS: We propose a mathematical model to estimate the evolution rate of the SARS coronavirus genome and the time of the last common ancestor of the sequenced SARS strains. Under some common assumptions and justifiable simplifications, a few simple equations incorporating the evolution rate (K) and time of the last common ancestor of the strains (T0) can be deduced. We then implemented the least square method to estimate K and T0 from the dataset of sequences and corresponding times. Monte Carlo stimulation was employed to discuss the results. RESULTS: Based on 6 strains with accurate dates of host death, we estimated the time of the last common ancestor to be about August or September 2002, and the evolution rate to be about 0.16 base/day, that is, the SARS coronavirus would on average change a base every seven days. We validated our method by dividing the strains into two groups, which coincided with the results from comparative genomics. CONCLUSION: The applied method is simple to implement and avoid the difficulty and subjectivity of choosing the root of phylogenetic tree. Based on 6 strains with accurate date of host death, we estimated a time of the last common ancestor, which is coincident with epidemic investigations, and an evolution rate in the same range as that reported for the HIV-1 virus.

China↗

Combining ultrasound and biochemistry in first-trimester screening for Down's syndrome.

Data on pregnancies with and without Down's syndrome between 10 and 14 weeks of pregnancy were used to determine the performance of combined ultrasound and biochemical markers in prenatal screening for Down's syndrome. We used three datasets: one published by Pandya et al. (1995) on nuchal translucency measurement in 86 Down's syndrome pregnancies; one published by Wald et al. (1996a) on free beta human chorionic gonadotrophin (hCG) and pregnancy-associated plasma protein A (PAPP-A) in 77 affected pregnancies and 385 unaffected pregnancies; and the third from Schuchter et al. on 561 unaffected pregnancies with nuchal translucency measurement. Combining the data from these three datasets showed that screening between 10 and 14 weeks by combining the serum markers with nuchal translucency measurement had a detection rate of 80 per cent for a 5 per cent false-positive rate, better than maternal age with two serum markers (62 per cent for 5 per cent) or maternal age with nuchal translucency measurement (63 per cent for 5 per cent). At this time in pregnancy, it appears that screening using the combined test is better than second-trimester serum screening (76 per cent for 5 per cent), though these estimates do not allow for any association between the markers and spontaneous fetal loss, an issue that needs to be clarified by further research. Meanwhile, these results provide a reasonable working estimate of screening performance using different combinations of these markers.

Chorionic Gonadotropin↗

Validation of clinical problems using a UMLS-based semantic parser.

The capture and symbolization of data from the clinical problem list facilitates the creation of high-fidelity patient resumes for use in aggregate analysis and decision support. We report on the development of a UMLS-based semantic parser and present a preliminary evaluation of the parser in the recognition and validation of disease-related clinical problems. We randomly sampled 20% of the 26,858 unique non-dictionary clinical problems entered into OMR (Online Medical Record) between 1989 and August, 1997, and eliminated a series of qualified problem labels, e.g., history-of, to obtain a dataset of 4122 problem labels. Within this dataset, the authors identified 2810 labels (68.2%) as referring to a broad range of disease-related processes. The parser correctly recognized and validated 1398 of the 2810 disease-related labels (49.8 +/- 1.9%) and correctly excluded 1220 of 1312 non-disease-related labels (93.0 +/- 1.4%). 812 of the 1181 match failures (68.8%) were caused by terms either absent from UMLS or modifiers not accepted by the parser; 369 match failures (31.2%) were caused by labels having patterns not recognized by the parser. By enriching the UMLS lexicon with terms commonly found in provider-entered labels, it appears that performance of the parser can be significantly enhanced over a few subsequent iterations. This initial evaluation provides a foundation from which to make principled additions to the UMLS lexicon locally for use in symbolizing clinical data; further research is necessary to determine applicability to other health care settings.

Medical Records Systems, Computerized↗

Evaluation of four in vitro genetic toxicity tests for predicting rodent carcinogenicity: confirmation of earlier results with 41 additional chemicals.

The effectiveness of four in vitro short-term tests (STT) for genetic toxicity, induction of mutations in Salmonella (SAL) and mouse lymphoma L5178Y cells (MLA), and induction of sister chromatid exchanges (SCE) and chromosome aberrations (ABS) in Chinese hamster ovary cells that are used for predicting rodent carcinogenicity were examined. The in vitro results were compared with the results from 41 rodent carcinogenicity studies performed by the National Toxicology Program. The predictive values of, and interrelationships among, the STT for these 41 chemicals were similar to those previously reported for 73 chemicals and confirm those earlier results [Tennant RW, Margolin BH, Shelby MD, Zeiger E, Haseman JK, Spalding J, Caspary W, Resnick M, Stasiewicz S, Anderson B, Minor R (1987): Science 236:933-941]. Because of this similarity among the two datasets, the chemicals were combined into a single dataset of 114. The results with 114 chemicals show that SAL had the lowest sensitivity (.48) and the highest specificity (.91), whereas MLA had the highest sensitivity (.72) and the lowest specificity (.40). The concordances of the test results with rodent carcinogenicity were .66, .61, .59, and .59, for SAL, ABS, SCE, and MLA, respectively. Salmonella was the most predictive for carcinogenicity; 89% of the chemicals mutagenic in SAL were carcinogenic in rodents, however a negative result in any or all of the STT was not indicative of noncarcinogenicity. The STT results reported here show good agreement with the potential electrophilicity of the chemicals, and the majority of carcinogens that are undetected by the STT do not have an electrophilic structure. There was no complementarity among the tests and no combination of the four tests was more effective than any single test for predicting carcinogenicity.

Animals↗

Looking at enzymes from the inside out: the proximity of catalytic residues to the molecular centroid can be used for detection of active sites and enzyme-ligand interfaces.

Analysis of the distances of the exposed residues in 175 enzymes from the centroids of the molecules indicates that catalytic residues are very often found among the 5% of residues closest to the enzyme centroid. This property of catalytic residues is implemented in a new prediction algorithm (named EnSite) for locating the active sites of enzymes and in a new scheme for re-ranking enzyme-ligand docking solutions. EnSite examines only 5% of the molecular surface (represented by surface dots) that is closest to the centroid, identifying continuous surface segments and ranking them by their area size. EnSite ranks the correct prediction 1-4 in 97% of the cases in a dataset of 65 monomeric enzymes (rank 1 for 89% of the cases) and in 86% of the cases in a dataset of 176 monomeric and multimeric enzymes from all six top-level enzyme classifications (rank 1 in 74% of the cases). Importantly, identification of buried or flat active sites is straightforward because EnSite "looks" at the molecular surface from the inside out. Detailed examination of the results indicates that the proximity of the catalytic residues to the centroid is a property of the functional unit, defined as the assembly of domains or chains that form the active site (in most cases the functional unit corresponds to a single whole polypeptide chain). Using the functional unit in the prediction further improves the results. The new property of active sites is also used for re-evaluating enzyme-inhibitor unbound docking results. Sorting the docking solutions by the distance of the interface to the centroid of the enzyme improves remarkably the ranks of nearly correct solutions compared to ranks based on geometric-electrostatic-hydrophobic complementarity scores.

Algorithms↗

Is there an association between maternal carbamazepine use during pregnancy and eye malformations in the child?

PURPOSE: To check for an association between carbamazepine (CBZ) use by the mother during pregnancy and congenital eye malformations (i.e., anophthalmia, microphthalmia, and coloboma) in the child, as suggested by Sutcliffe et al. (1998), who reported four cases. METHODS: We checked all the cases with these eye malformations for CBZ use by the mother in the EUROCAT Northern Netherlands dataset, which registers infants with congenital malformations and records possible teratogenic exposures (including medication taken by the mother). We also reviewed 13 studies in the literature. RESULTS: The EUROCAT dataset recorded 77 cases of anophthalmia, microphthalmia, or coloboma, but none with prenatal exposure to CBZ. Prenatal CBZ exposure was recorded in seven other cases without congenital eye malformation. Large studies in the literature on the teratogenic effects of CBZ (and other antiepileptic drugs), including data from the MADRE database, revealed no association between these congenital eye malformations and prenatal CBZ exposure. One case reported bilateral anophthalmia and other congenital anomalies after prenatal exposure to CBZ in combination with vigabatrin and dexamethasone. CONCLUSIONS: Our data do not support Sutcliffe's suggestion that prenatal CBZ exposure may result in congenital eye malformations. However, despite the large population represented, both the low birth prevalence of these congenital eye malformations and the low prevalence of CBZ exposure during pregnancy make it difficult to exclude an increased relative risk. The many large prospective and retrospective studies in the literature seem to agree with our findings, although there is still uncertainty about the teratogenic effect of CBZ in polytherapy.

Carbamazepine↗

Determinants of the intracluster correlation coefficient in cluster randomized trials: the case of implementation research.

The objective of this research was to identify determinants of the magnitude of intracluster correlation coefficients (ICCs) in cluster randomized trials from the field of implementation research. A survey of experts was conducted to generate a priori hypotheses of factors that might affect ICC size. Hypotheses were tested on empirical estimates of ICCs calculated from 21 implementation research datasets, mainly from the UK. Effects of setting (primary or secondary care), type of variable (process or outcome), type of measurement (objective or subjective), prevalence of outcome and size of cluster were tested. In total, 220 ICCs were available (range 0 to 0.415). Significant differences in ICC magnitude were found. The ICCs were significantly higher for process than for outcome variables, and for secondary care outcomes compared with primary care outcomes. The effects of prevalence and size were less clear cut. There was no evidence to suggest that type of measurement affected ICC size. In conclusion, accurate estimates of ICCs are essential for sample size calculations for cluster randomized trials of professional behaviour change interventions. This study demonstrates that ICCs are sensitive to a number of trial factors, particularly setting and outcome type. These factors must be considered when planning such cluster randomized trials.

Biomedical Research↗