Improving the external validity of Antenatal Late Preterm Steroids trial findings

When, why and how are estimated effects transported between populations? A scoping review of studies applying transportability methods

Transportability methods can improve the external validity of estimated effects by accounting for effect heterogeneity due to differently distributed covariates between populations. This scoping review aims to provide an overview of when, why and how transportability methods have been applied. We systematically searched MEDLINE (Ovid), Embase, Web of Science, EconLit and Google Scholar for studies published between 2010 and December 18, 2024. Studies using transportability methods in a numerical application for at least partly non-overlapping source and target populations were included. We identified 3432 unique studies and included 64 studies applying transportability methods. Over two thirds of the included studies (44/64) introduced new methods. Less than one third of the included studies (20/64) were pure applications of transportability methods. Most applied studies (17/20) transported effect estimates from randomized controlled trials. Effects were transported to target populations with either complete (9/20) or no (9/20) treatment and outcome data or both (2/20). The most frequent aims of applied studies were to transport estimated effects to new populations (10/20) and to assess effect heterogeneity explainable by measured covariates (8/20). How transportability methods were applied varied widely between studies, for instance in the covariate selection approach and sensitivity analysis. Methodological studies with a transportability application presented new transportability estimators for randomized data (5/44), specific transportability applications (e.g., meta-analysis, mediation analysis; 21/44) and other methodological aspects (e.g., covariate selection, missing data handling; 18/44). Transportability methods are a useful tool for knowledge transfer between populations. More applications of transportability methods and guidance for their use are desirable.

Systematic review of applied transportability and generalizability analyses: A landscape analysis

Transportability and generalizability analysis are novel causal inference methods that quantitatively assess external validity. Currently, it is unclear how these analyses are applied in practice. To characterize applications and methods, we conducted a landscape analysis of applied transportability and generalizability analyses using a systematic literature search of PubMed, CINAHL and Embase supplemented with hand-searches. We identified 68 publications describing transportability and generalizability analyses conducted with 83 unique source-target dataset pairs and reporting 99 distinct analyses. The majority of source and target datasets were collected in the US (n = 63/83, 75.9 %; and n = 59/83, 71.1 %, respectively). These methods were most often applied to transport RCT findings to observational studies (n = 38/83; 45.8 %), or to another RCT (n = 20/83; 24.1 %). Several studies used transportability analysis outside the standard application, for example to identify effect modifiers or calibrate measurements within an RCT. Methods that used weights and individual-level patient data were most common (n = 56/99, 56.5 %; n = 80/83, 96.4 %, respectively). Reporting quality varied across studies. Transportability analysis has a wide range of applications including supporting decision-making by improving evidence relevance and improving trial design by identifying contextual effect modifiers and calibrating outcome measurements. Efforts are needed to standardize analysis and reporting of these methods to improve transparency and uptake.

Randomized controlled trials: not always the "gold standard" for evidence in obstetrics and gynecology

Randomized controlled trials are considered the "gold standard" for therapeutic interventions, and it is not uncommon for sweeping changes in medical practice to follow positive results from such trials. However, randomized controlled trials are not without their limitations. Physicians frequently view randomized controlled trials as infallible, whereas they tend to dismiss evidence derived from sources other than randomized controlled trials as less credible or reliable. In several situations in obstetrics and gynecology, there are no randomized controlled trials to help guide the clinician. In these circumstances, it is important to evaluate the entire body of evidence including observational studies, rather than dismiss interventions altogether simply because no randomized controlled trials exist. Randomized controlled trials and observational studies should be viewed as complementary rather than at odds with each other. Some reversals in widely adopted clinical practice have recently been implemented following subsequent studies that contradicted the outcomes of major randomized controlled trials. The most notable of these was the withdrawal from the market of 17-hydroxyprogesterone caproate for preterm birth prevention. Such reversals could potentially have been averted if the inherent limitations of randomized controlled trials were carefully considered before implementing these universal practice changes. This Clinical Opinion underscores the limitations of an exclusive reliance on randomized controlled trials while disregarding other evidence in determining how best to care for patients. Solutions are proposed that advocate that clinicians adopt a more balanced perspective that considers the entirety of the available medical evidence and the individual patient characteristics, needs, and wishes.

Antenatal corticosteroid treatment and infectious diseases in children: a nationwide observational study

Background

Antenatal Corticosteroid Treatment (ACT) improves the outcome of preterm infants, but may influence immune system development and risk of immune-related diseases. We investigated whether ACT is associated with infectious diseases in children born at term (≥37 gestational weeks), and very-to-moderate (<34 gestational weeks), and late (34-36 completed gestational weeks) preterm.

Methods

All singleton live births in Finland between 01/01/2006 and 31/12/2021, were followed-up until 31/12/2021. Exposure was maternal ACT. Primary outcomes were numbers of inpatient treatment days, episodes, and specialized care outpatient visits with any infectious disease diagnoses between ages 0 and 4 years. We considered mother- and child-related covariates, and conducted term-born co-sibling comparisons.

Findings

Data comprised 855,234 children. Of the 20,858 (2.4%) treatment-exposed children, 5981 (28.2%) were very-to-moderate preterm-born, 5809 (27.9%) late preterm-born, and 9069 (43.5%) term-born. Of the 271,767 term-born co-sibling pairs, 5010 (1.8%) were treatment-exposure-discordant, and 266,522 (98.1%) nonexposure-concordant. Among the term- and late preterm-born, treatment-exposed children had more inpatient treatment days than nonexposed children (term: 0.87 vs. 0.56 day/y, adjusted mean difference [aMD] 0.19, 95% CI 0.17-0.28; late preterm: 1.35 vs. 1.00 days/y, aMD 0.31,0.13-0.31), more inpatient treatment episodes (term: 0.43 vs. 0.33 episodes/y, aMD 0.06, 0.06-0.11; late preterm: 0.55 vs. 0.48 episodes/y, aMD 0.12, 0.06-0.18), and specialized care treatment visits (term: 1.46 vs. 0.95 visits/y, aMD 0.38; 0.34-0.43; late preterm: 1.63 vs. 1.28 visits/y, aMD 0.22, 0.12-0.32). Treatment-exposed and nonexposed very-to-moderate preterm-born children were similar in these outcomes, though they had less inpatient treatment days and episodes at 3-4 years. Differences remained in term-born co-sibling comparisons.

Interpretation

These findings reinforce previous suggestions for careful consideration of risks and benefits of ACT.

Funding

Academy of Finland, HiLIFE Fellows-Programme.

Technical Update No. 439: Antenatal Corticosteroids at Late Preterm Gestation

OBJECTIVE

To update recommendations for administration of antenatal corticosteroids in the late preterm period.

TARGET POPULATION

Pregnant individuals at risk of preterm birth from 340 to 366 weeks gestation.

OPTIONS

Administration or non-administration of a single course of antenatal corticosteroids at 340 to 366 weeks gestation.

OUTCOMES

Neonatal morbidity (respiratory distress, hypoglycemia), long-term neurodevelopment, and other long-term outcomes (growth, cardiac/metabolic, respiratory).

BENEFITS, HARMS, AND COSTS

Administration of antenatal corticosteroids from 340 to 366 weeks gestation decreases the risk of neonatal respiratory distress but increases the risk of neonatal hypoglycemia. The long-term impacts of antenatal corticosteroid administration from 340 to 366 weeks gestation are uncertain.

EVIDENCE

For evidence on the neonatal effects of antenatal corticosteroid administration at late preterm gestation, we summarized evidence from the 2020 Cochrane review of antenatal corticosteroids and combined this with evidence from published randomized trials identified by searching Ovid MEDLINE from January 1, 2020, to May 11, 2022. Given the absence of direct evidence on the impact of late preterm antenatal corticosteroid administration on neurodevelopmental outcomes, we summarized evidence on the impact of antenatal corticosteroids across gestational ages on neurodevelopmental outcomes using the following sources: (1) the 2020 Cochrane review; and (2) evidence obtained by searching Ovid MEDLINE, Embase, and Cochrane Central Register of Controlled Trials (CENTRAL) databases from inception to January 5, 2022. We did not apply date or language restrictions. Given the absence of direct evidence on the impact of late preterm antenatal corticosteroid administration on other long-term outcomes, we summarized evidence on the impact of antenatal corticosteroids across gestational ages on other long-term outcomes by combining findings from the 2020 Cochrane review with evidence obtained by searching Ovid MEDLINE for observational studies related to long-term cardiometabolic, respiratory, and growth effects of antenatal corticosteroids from inception to October 22, 2021. We reviewed reference lists of included studies and relevant systematic reviews for additional references. See Appendix A for search terms and summaries.

VALIDATION METHODS

The authors rated the quality of evidence and strength of recommendations using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. See online Appendix B (Tables B1 for definitions and B2 for interpretations of strong and conditional [weak] recommendations).

INTENDED AUDIENCE

Maternity care providers, including midwives, family physicians, and obstetricians.

SUMMARY STATEMENTS

RECOMMENDATIONS.