Editorial statistics

Development and application of statistical models for medical scientific researc

Editorial statistics

Development and application of statistical models for medical scientific researc

External validation of a dynamic prediction model for repeated predictions of natural conception over time

This work was supported by a Chief Scientist Office postdoctoral training fellowship in health services research and health of the public research (ref PDF/12/06). There are no conflicts of interest.Peer reviewedPostprin

IVF for unexplained subfertility : whom should we treat?

Acknowledgements The authors would like to thank Tenovus Scotland and the Amsterdam Reproduction & Development Research Group for funding this project. We acknowledge the data management support of the Grampian Data Safe Haven (DaSH) and the associated financial support of NHS Research Scotland, through NHS Grampian investment in the Grampian DaSH. For more information, visit the DaSH website http://www.abdn.ac.uk/iahs/facilities/grampian-data-safe-haven.php. Funding Tenovus Scotland [grant G17.04], travel was supported by the Amsterdam Reproduction & Development Research Group [grant V.000296 to RvE].Peer reviewedPostprin

Choosing and changing the analysis scale in non-inferiority trials with a binary outcome

Algorithms and the Foundations of Software technolog

Birthweight of children with isolated congenital heart disease: a sibling analysis study

ObjectiveCongenital heart disease (CHD) is associated with decreased birthweight (BW) compared to population-based references. The aim of this study was to compare the BW of isolated CHD cases to their siblings, thus controlling for unknown and unmeasured confounders within the family. MethodsAll isolated CHD cases in the Leiden University Medical Center were included (2002-2019). Generalized estimated equation models were constructed to compare BW z scores of CHD neonates with their siblings. Cases were clustered to minor or severe CHD and stratified according to the aortic flow and oxygenation to the brain. ResultsThe overall BW z score of siblings was 0.032 (n = 471). The BW z score was significantly lower in CHD cases (n = 291) compared to their siblings (-0.20, p = 0.005). The results were consistent in the subgroup analysis of severe and minor CHD (BW z score difference -0.20 and -0.10), but did not differ significantly (p = 0.63). Stratified analysis regarding flow and oxygenation showed no BW difference between the groups (p = 0.1). ConclusionIsolated CHD cases display a significantly lower BW z score compared to their siblings. As the siblings of these CHD cases show a BW distribution similar to the general population, this suggests that shared environmental and maternal influences between siblings do not explain the difference in BW.Research into fetal development and medicin

Low Hartmann’s procedure or intersphincteric proctectomy for distal rectal cancer: a retrospective comparative cohort study

Purpose: Two non-restorative options for low rectal cancer not invading the sphincter are the low Hartmann’s procedure (LH) or intersphincteric proctectomy (IP). The aim of this study was to compare postoperative morbidity with emphasis on pelvic abscesses after LH and IP. Methods: All patients that had LH or IP for low rectal cancer were included in three centres between 2008 and 2014 in this retrospective cohort study. Follow-up was performed for at least 12 months. Results: A total of 52 patients were included: 40 LH and 12 IP. Median follow-up was 29 months (IQR 23). There were no differences between groups in gender, age and ASA classification. Seven patients in the LH group (18%) and four patients in the IP group (33%) developed a complication within 30-day postoperative with a Clavien-Dindo classification grade III or higher (P = 0.253). Four out of 40 patients (10%) in the LH group and two out of 12 patients (17%) in the IP group developed a pelvic abscess (P = 0.612). Reinterventions were performed in 11 (28%) patients in the LH group and five (42%) patients in the IP group (P = 0.478), with a total number of reinterventions of 13 and 20, respectively. Six and 15 interventions were related to pelvic abscesses, respectively. Conclusion: Pelvic abscesses seem to occur in a similar rate after both LH and IP. Previous reports from the literature suggesting that IP might be associated with less infectious pelvic complications compared to LH are not supported by this study, although numbers are small

Lessons learnt when accounting for competing events in the external validation of time-to-event prognostic models.

BACKGROUND: External validation of prognostic models is necessary to assess the accuracy and generalizability of the model to new patients. If models are validated in a setting in which competing events occur, these competing risks should be accounted for when comparing predicted risks to observed outcomes. METHODS: We discuss existing measures of calibration and discrimination that incorporate competing events for time-to-event models. These methods are illustrated using a clinical-data example concerning the prediction of kidney failure in a population with advanced chronic kidney disease (CKD), using the guideline-recommended Kidney Failure Risk Equation (KFRE). The KFRE was developed using Cox regression in a diverse population of CKD patients and has been proposed for use in patients with advanced CKD in whom death is a frequent competing event. RESULTS: When validating the 5-year KFRE with methods that account for competing events, it becomes apparent that the 5-year KFRE considerably overestimates the real-world risk of kidney failure. The absolute overestimation was 10%age points on average and 29%age points in older high-risk patients. CONCLUSIONS: It is crucial that competing events are accounted for during external validation to provide a more reliable assessment the performance of a model in clinical settings in which competing risks occur