Cristina Costa-Santos

The limits of agreement and the intraclass correlation coefficient may be inconsistent in the interpretation of agreement.

OBJECTIVE To compare the interpretation of agreement in the prediction of neonatal outcome variables, using the limits of agreement (LA) and the intraclass correlation coefficient (ICC). STUDY DESIGN AND SETTING Three obstetricians were asked to predict neonatal outcomes independently based on the evaluation of intrapartum cardiotocographic tracings. Interobserver agreement was assessed with the LA and the ICC, and the results obtained were interpreted by six clinicians and six statisticians on a scale that established agreement as very poor, poor, fair, good, or very good. RESULTS Interpretation of the LA results was less consensual than the ICC results, with proportions of agreement of 0.36 (95% confidence interval [CI]: 0.28-0.44) vs. 0.63 (95% CI: 0.54-0.73), respectively. LA results suggested a fair to good agreement among obstetricians, whereas interpretation of ICC results suggested a poor to fair agreement. LA results were more plausible with reality, suggesting that obstetricians predicted neonatal outcomes better than randomly generated values, whereas it was not always the case with the ICC. CONCLUSIONS LA and ICC can provide inconsistent results in agreement studies. Accordingly, in the absence of better strategies to assess agreement, both should be used for this purpose, but their results need to be interpreted with caution keeping their respective limitations in mind.

The modified Misgav-Ladach versus the Pfannenstiel–Kerr technique for cesarean section: a randomized trial

Background.  Modifications to the classic cesarean section technique described by Pfannenstiel and Kerr have been proposed in the last few years. The objective of this trial was to compare intraoperative and short‐term postoperative outcomes between the Pfannenstiel–Kerr and the modified Misgav‐Ladach (MML) techniques for cesarean section.

Occupational factors and risk of adult bone sarcomas: A multicentric case-control study in Europe

We investigated the association between occupational factors and risk of bone sarcoma, a rare tumor with a largely unknown aetiology. A multicentric case‐control study was conducted in 7 European countries in 1995–97. Ninety‐six cases aged 35–69 years with a centrally reviewed diagnosis of bone sarcoma (68 chondrosarcomas and 28 osteosarcomas) were compared to 2,632 population (68%) or colon cancer (32%) controls. Subjects were interviewed to obtain information on occupational, medical and reproductive history, smoking and alcohol consumption and selected exposures including use of pesticides. Response proportions were 90% among cases and 66% among controls. Odds ratios (OR) and 95% confidence intervals (CI) were estimated for selected categories of job titles and branches of industry and for use of pesticides. We found an increased OR for bone sarcoma among blacksmiths, toolmakers, machine‐tool operators (OR = 2.14, 95% CI 1.08–4.26), woodworkers (OR = 2.68, 95% CI 1.36–5.29) and construction workers (OR = 1.62, 95% CI 0.92–2.87). Ever users of pesticide had an OR of 2.33 (95% CI 1.31–4.13), with similar risks for exposure to insecticides and exposure to herbicides. Neither duration of employment in any of the analyzed occupational categories nor duration of use of pesticides showed an increasing trend in the risk of bone sarcoma. ORs of bone sarcoma were 1.03 (95% CI 0.23–4.57), 3.13 (95% CI 1.26–7.76) and 1.44 (95% CI 0.43–4.85) for the first, second and third tertile of days of use of pesticides. Our study suggests that novel and previously reported (woodworking) occupational factors play a role in the aetiology of bone sarcomas.

Knowledge of adverse neonatal outcome alters clinicians’ interpretation of the intrapartum cardiotocograph

Please cite this paper as: Ayres‐de‐Campos D, Arteiro D, Costa‐Santos C, Bernardes J. Knowledge of adverse neonatal outcome alters clinicians’ interpretation of the intrapartum cardiotocograph. BJOG 2011;978:985–984.

Assessment of Disagreement: A New Information-Based Approach

PURPOSE Disagreement on the interpretation of diagnostic tests and clinical decisions remains an important problem in medicine. As no strategy to assess agreement seems to be fail-safe to compare the degree of agreement, or disagreement, we propose a new information-based approach to assess disagreement. METHODS The sum over all logarithms of possible outcomes of a variable is a valid measure of the amount of information contained in the variable. The proposed measure is based on the amount of information contained in the differences between two observations. This measure is normalized and satisfies the flowing properties: it is a metric, scaled invariant and it has differential weighting. RESULTS Two real examples and a simulation were used to illustrate the usefulness of the proposed measure to compare the degree of disagreement. CONCLUSIONS Used as complement to the existing methods, we believe our approach can be useful to compare the degree of disagreement among different populations.

Development and evaluation of an algorithm for computer analysis of maternal heart rate during labor

BACKGROUND Maternal heart rate (MHR) recordings are morphologically similar and sometimes coincident with fetal heart rate (FHR) recordings and may be useful for maternal-fetal monitoring if appropriately interpreted. However, similarly to FHR, visual interpretation of MHR features may be poorly reproducible. METHODS A computer algorithm for on-line MHR analysis was developed based on a previously existing version for FHR analysis. Inter-observer and computer-observer agreement and reliability were assessed in 40 one-hour recordings obtained from 20 women during the last 2h of labor. Agreement and reliability were evaluated for the detection of basal MHR, long-term variability (LTV), accelerations and decelerations, using proportions of agreement (PA) and Kappa statistic (K), with 95% confidence intervals (95% CI). Changes in MHR characteristics between the first and the second hour of the tracings were also evaluated. RESULTS There was a statistically significant inter-observer and computer-observer agreement and reliability in estimation of basal MHR, accelerations, decelerations and LTV, with PA values ranging from 0.72 (95% CI: 0.62-0.79) to 1.00 (95% CI: 0.99-1.00), and K values ranging from 0.44 (95% CI: 0.28-0.60) to 0.89 (95% CI: 0.82-0.96). Moreover, basal MHR, number of accelerations and LTV were significantly higher in the last hour of labor, when compared to the initial hour. DISCUSSION The developed algorithm for on-line computer analysis of MHR recordings provided good to excellent computer-observer agreement and reliability. Moreover, it allowed an objective detection of MHR changes associated with labor progression, providing more information about the interpretation of maternal-fetal monitoring during labor.

Entropy and compression: two measures of complexity.

RATIONALE, AIMS AND OBJECTIVES Traditional complexity measures are used to capture the amount of structured information present in a certain phenomenon. Several approaches developed to facilitate the characterization of complexity have been described in the related literature. Fetal heart rate (FHR) monitoring has been used and improved during the last decades. The importance of these studies lies on an attempt to predict the fetus outcome, but complexity measures are not yet established in clinical practice. In this study, we have focused on two conceptually different measures: Shannon entropy, a probabilistic approach, and Kolmogorov complexity, an algorithmic approach. The main aim of the current investigation was to show that approximation to Kolmogorov complexity through different compressors, although applied to a lesser extent, may be as useful as Shannon entropy calculated by approximation through different entropies, which has been successfully applied to different scientific areas. METHODS To illustrate the applicability of both approaches, two entropy measures, approximate and sample entropy, and two compressors, paq8l and bzip2, were considered. These indices were applied to FHR tracings pertaining to a dataset composed of 48 delivered fetuses with umbilical artery blood (UAB) pH in the normal range (pH ≥ 7.20), 10 delivered mildly acidemic fetuses and 10 moderate-to-severe acidemic fetuses. The complexity indices were computed on the initial and final segments of the last hour of labour, considering 5- and 10-minute segments. RESULTS In our sample set, both entropies and compressors were successfully utilized to distinguish fetuses at risk of hypoxia from healthy ones. Fetuses with lower UAB pH presented significantly lower entropy and compression indices, more markedly in the final segments. CONCLUSIONS The combination of these conceptually different measures appeared to present an improved approach in the characterization of different pathophysiological states, reinforcing the theory that entropies and compressors measure different complexity features. In view of these findings, we recommend a combination of the two approaches.

Lowered national cesarean section rates after a concerted action

To evaluate national cesarean section (CS) rates and other obstetric indicators after a concerted action to reduce CS rates was undertaken in Portugal from 2010 onwards. This action was based on the transmission of information and training of healthcare professionals, together with the inclusion of CS rates as a criterion for hospital funding.

Information-based measure of disagreement for more than two observers: a useful tool to compare the degree of observer disagreement.

BackgroundAssessment of disagreement among multiple measurements for the same subject by different observers remains an important problem in medicine. Several measures have been applied to assess observer agreement. However, problems arise when comparing the degree of observer agreement among different methods, populations or circumstances.MethodsThe recently introduced information-based measure of disagreement (IBMD) is a useful tool for comparing the degree of observer disagreement. Since the proposed IBMD assesses disagreement between two observers only, we generalized this measure to include more than two observers.ResultsTwo examples (one with real data and the other with hypothetical data) were employed to illustrate the utility of the proposed measure in comparing the degree of disagreement.ConclusionThe IBMD allows comparison of the disagreement in non-negative ratio scales across different populations and the generalization presents a solution to evaluate data with different number of observers for different cases, an important issue in real situations.A website for online calculation of IBMD and respective 95% confidence interval was additionally developed. The website is widely available to mathematicians, epidemiologists and physicians to facilitate easy application of this statistical strategy to their own data.

Longitudinal evaluation of computerized cardiotocographic parameters throughout pregnancy in normal fetuses: a prospective cohort study.

The longitudinal cardiotocographic (CTG) changes throughout pregnancy in normal fetuses have never been fully described. We aimed at characterizing the evolution of CTG parameters in healthy fetuses, from 24 to 41 weeks of gestation.