Emulating Target Trials to Avoid Immortal Time Bias - An Application to Antibiotic Initiation and Preterm Delivery

Hospital-Onset Bacteremia Among Neonatal Intensive Care Unit Patients

Importance

The Centers for Disease Control and Prevention plans to introduce hospital-onset bacteremia (HOB) as a health care-associated infection measure. The epidemiology and clinical characteristics of HOB among infants admitted to the neonatal intensive care unit (NICU) are unknown.

Objective

To estimate the rate of HOB among infants admitted to the NICU, measure the association of HOB risk with birth weight group and postnatal age, and estimate HOB-attributable mortality.

Design, Setting, and Participants

This retrospective multicenter cohort study and emulated trial from 2016 to 2021 included a convenience sample of 322 NICUs in the United States. Participants were infants admitted to participating NICUs for 4 or more days.

Exposures

The primary exposures were birth weight and postnatal age. Additional exposures included small for gestational age and central line presence.

Main Outcomes and Measures

The primary study outcomes were HOB and HOB-attributable mortality.

Results

Of 451 443 included infants, 250 763 (55.6%) were male, 200 680 (44.4%) were female, and 62 091 (13.8%) were born 1500 g or less. Of 9015 HOB events that occurred among 8356 infants (2%) during 8 163 432 days at risk (unadjusted incidence rate, 1.1 per 1000 patient-days; 95% CI, 1.0-1.2), 4888 HOB events (54.2%) occurred in the absence of a central line. Within the first 2 weeks after birth, the HOB rate was 14.2 per 1000 patient-days (95% CI, 12.6-16.1) among infants born 750 g or less, to 0.4 events per 1000 patient-days among infants born more than 2500 g (95% CI, 0.4-0.5). Among infants born 750 g or less, the relative HOB risk decreased by 90% after day 42 compared with days 4 to 14 (incidence rate ratio [IRR], 0.10; 95% CI, 0.1-0.1). Conversely, among infants born more than 2500 g, the relative HOB risk increased by 50% after day 42 compared with days 4 to 14 (IRR, 1.5, 95% CI, 1.2-1.9). Compared with otherwise similar infants without HOB, infants with HOB had an absolute difference in attributable mortality of 5.5% (95% CI, 4.7-6.3).

Conclusions and Relevance

This study found that HOB events in the NICU are associated with increased mortality. Birth weight is an important risk factor for HOB; however, the relative rate of HOB decreases over postnatal age among low-birth-weight infants and increases among infants born more than 2500 g. Identifying strategies to prevent HOB and programs to decrease HOB risk are urgently needed to reduce infant mortality.

Use of leflunomide among girls and women of childbearing age and occurrence of leflunomide-exposed pregnancies in Germany

Leflunomide is contraindicated during pregnancy and treatment cessation is recommended two years before pregnancy. We aimed to describe leflunomide use in women of childbearing age in Germany, the occurrence of pregnancies in women using leflunomide and malformations among children possibly exposed in utero. Using the GePaRD database (claims data, ∼20% of the German population), we determined annual age-standardized prevalences of leflunomide use between 2004 and 2019 among females aged 13-49 years. Further, we estimated the number of exposed pregnancies by assessing whether the exposure window assigned to the last dispensation before pregnancy (days covered by the dispensation plus two years) overlapped the onset of pregnancy or whether there was a dispensation in the first eight weeks of pregnancy. For exposed live births, a mother-baby linkage was performed and the presence of congenital malformation was assessed. The age-standardized prevalence of leflunomide use ranged between 0.34 and 0.46 per 1000 females during the study period. About one third of the users were ≤40 years. We identified 205 leflunomide-exposed pregnancies ending during the study period. 71% of these pregnancies ended in a live birth (26% preterm) and 10% in an induced abortion. In 86% of the live births (n=125) the mother-baby linkage was successful. Among these 125 children, 13 children (10%) had congenital malformations. In conclusion, we observed a considerable number of pregnancies in women using leflunomide in the two years before or during early pregnancy. This highlights the importance of monitoring the implementation of existing risk minimization measures for leflunomide in Germany.

Levothyroxine initiation and the risk of pregnancy loss among pregnant women with subclinical hypothyroidism: An observational study emulating a target trial

BACKGROUND

While the benefits of levothyroxine are well-established for overt hypothyroidism, they are unclear for subclinical hypothyroidism (SCH) among pregnant women.

OBJECTIVE

To estimate the effect of initiation of levothyroxine on pregnancy loss among women with SCH with an emulated target trial using observational data.

METHODS

We emulated a target trial using the United Kingdom's Clinical Practice Research Datalink to account for the staggered timing of diagnosis and treatment of SCH and the time of entry of women into prenatal care. We emulated multiple nested trials (at each gestational week) and used an intention-to-treat approach to define levothyroxine use (≥1 prescription in the 7 days prior to trial entry), with eligible users matched to non-users (1:4) on time of diagnosis, gestational week of the first eligible trial and high-dimensional propensity score. Pregnancy losses included spontaneous abortion and stillbirth. A pooled logistic regression model with bootstrap resampling was used to estimate the hazard ratios (HR) and 95% confidence intervals (CI).

RESULTS

Based on 159,177 eligible person-trials (5781 women), the matched cohort included 181 initiators and 640 non-initiators of levothyroxine, with 57 pregnancy losses occurring during follow-up. Overall, the mean age of women was 32.2 years (SD 5.4), 25% were obese, 8% had type 2 diabetes and about 50% were nulliparous. After matching, women who initiated levothyroxine versus not had higher thyroid-stimulating levels during pregnancy and were more likely to have a history of hypothyroidism. The cumulative incidence of pregnancy loss was lower in initiators versus non-initiators of levothyroxine. The adjusted HR for pregnancy loss was 0.87 (95% CI 0.22, 1.56).

CONCLUSIONS

Although our assessment of the effect of initiation of levothyroxine for SCH in pregnancy precludes any definitive conclusions due to wide confidence intervals, this study illustrates the feasibility of using the target trial emulation framework to examine the effectiveness of medication use in pregnancy.

Offspring neurodevelopmental outcomes born to parents with chronic inflammatory arthritis using antirheumatic therapies: A scoping review

INTRODUCTION

Most women with rheumatic diseases discontinue antirheumatic therapies in anticipation of, or during pregnancy due to concerns around medication safety and fetal wellbeing.

OBJECTIVE

We performed a scoping review of available evidence investigating the risks of adverse offspring neurodevelopmental outcomes amongst parents with chronic inflammatory arthritis, taking antirheumatic therapies during conception or pregnancy.

METHODS

We designed a scoping review protocol and search strategy a priori in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We performed an exhaustive search in Cochrane Library, Embase, Google Scholar, Medline, and Web of Science for relevant literature in January 2023. Articles needed to include offspring neurodevelopmental outcomes born to parents with CIA who took antirheumatic therapies during conception or pregnancy. Independent reviewers extracted data from eligible articles using a standard abstraction tool and performed critical appraisal of study quality.

RESULTS

Six studies were included for full data abstraction. Use of Nonsteroidal Anti-inflammatory Drugs, Tumor Necrosis Factor Alpha inhibitors, and exposure to methotrexate during early first trimester of pregnancy did not seem to increase risk for adverse offspring neurodevelopmental outcomes. Corticosteroid use during pregnancy seemed to pose an increased risk for attention deficit hyperactive disorders in offspring.

CONCLUSION

Use of some antirheumatic therapies during pregnancy may not be associated with adverse offspring neurodevelopmental outcomes. Further investigations are needed to elucidate if other confounding factors affect long term offspring health outcomes born to parents with chronic inflammatory arthritis.

Effect of Nirmatrelvir/Ritonavir (Paxlovid) on Hospitalization among Adults with COVID-19: an EHR-based Target Trial Emulation from N3C

This study leverages electronic health record data in the National COVID Cohort Collaborative's (N3C) repository to investigate disparities in Paxlovid treatment and to emulate a target trial assessing its effectiveness in reducing COVID-19 hospitalization rates. From an eligible population of 632,822 COVID-19 patients seen at 33 clinical sites across the United States between December 23, 2021 and December 31, 2022, patients were matched across observed treatment groups, yielding an analytical sample of 410,642 patients. We estimate a 65% reduced odds of hospitalization among Paxlovid-treated patients within a 28-day follow-up period, and this effect did not vary by patient vaccination status. Notably, we observe disparities in Paxlovid treatment, with lower rates among Black and Hispanic or Latino patients, and within socially vulnerable communities. Ours is the largest study of Paxlovid's real-world effectiveness to date, and our primary findings are consistent with previous randomized control trials and real-world studies.