Estimating average treatment effects for clustered RCTs with recruitment bias.

In clustered randomized controlled trials (RCTs), sample recruitment is often conducted after cluster randomization. This timing can lead to recruitment bias if access to the intervention affects the composition of study-eligible cluster entrants and study consenters. This article develops a potential outcomes framework in such settings that yields a causal estimand that pertains to the always-recruited in either research condition. A consistent inverse probability weighting (IPW) estimator is developed using data on recruits only, and a generalized estimating equations approach is used to obtain robust clustered SE estimators that adjust for estimation error in the IPW weights. A simple data collection strategy is discussed to improve the predictive accuracy of the logit propensity score models. Simulations show that the IPW estimator achieves nominal confidence interval coverage under the assumed identification conditions. An empirical application demonstrates the methods using data from an RCT testing the effects of a behavioral health intervention in schools. An R program for estimation is available for download.

The Complier Average Causal Effect Parameter for Multiarmed RCTs.

In randomized controlled trials, the complier average causal effect (CACE) parameter is often of policy interest because it pertains to intervention effects for study units that comply with their research assignments and receive a meaningful dose of treatment services. Causal inference methods for identifying and estimating the CACE parameter using an instrumental variables (IV) framework are well established for designs with a single treatment and control group. This article uses a parallel IV framework to discuss and build on the much smaller literature on estimation of CACE parameters for designs with multiple treatment groups. The key finding is that the conditions to identify and estimate CACE parameters are much more complex for multiarmed designs and may not be tractable in some cases. Practical steps are provided on how to proceed, and a case study demonstrates key issues. The results suggest that ensuring compliance is particularly important in multiarmed trials so that intention-to-treat estimates on the offer of intervention services (which can be identified) can provide meaningful information on the CACE parameters.

Radiographic, Pulmonary, and Clinical Outcomes With Halo Gravity Traction.

STUDY DESIGN: Single-center retrospective chart review. OBJECTIVES AND SUMMARY: Halo gravity traction (HGT) is a safe and effective intervention to improve spinal deformity prior to corrective instrumentation. Our study aimed to report on a large series of patients undergoing HGT, demonstrate the correlation between thoracic height achieved and pulmonary function, and evaluate the efficacy of nutritional assessment and intervention while in HGT for these often malnourished or nutritionally compromised patients. METHODS: 107 patients underwent HGT for severe spinal deformity. Major coronal and sagittal Cobb angles, T1-T12 ht, and T1-S1 ht were collected pre-HGT, during HGT, postoperation, and 2 years postoperation. Pulmonary function tests (PFTs) recorded forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1). Nutritional interventions such as formal nutrition consult, resulting nutritional supplementation, or interventions were recorded. RESULTS: Patients were in HGT for mean of 82.1 days and mean maximum percentage body weight in traction was 49.5%. Mean major coronal Cobb angle prior to HGT was 92.6°, improving to 65.8° in maximal traction and to 47° after surgical intervention. Traction accounted for 78% of T1-T12 height and 79% of T1-S1 length gains from pre- to postoperation. We showed a positive correlation between gain in T1-T12 height and percentage predicted changes in FVC and FEV1. Weight Z score for the entire cohort of patients improved from -2.8 pretraction to -2.4 in traction and then to -2.3 postoperative. CONCLUSIONS: Our study again demonstrated that HGT achieves radiographic improvement safely and effectively in severe spinal deformity. We demonstrated a positive correlation between improvement in PFTs and increase in thoracic height seen with HGT. Additionally, improvement in weight Z score was seen in the entire population and the most at risk patients for malnutrition, results that have not been shown before. LEVEL OF EVIDENCE: Level IV.

An approach for addressing the multiple testing problem in social policy impact evaluations.

In social policy evaluations, the multiple testing problem occurs due to the many hypothesis tests that are typically conducted across multiple outcomes and subgroups, which can lead to spurious impact findings. This article discusses a framework for addressing this problem that balances Types I and II errors. The framework involves specifying confirmatory and exploratory analyses in study protocols, delineating confirmatory outcome domains, conducting t tests on composite domain outcomes, and applying multiplicity corrections to composites across domains to obtain summative impact evidence. The article presents statistical background and discusses multiplicity issues for subgroup analyses, designs with multiple treatments, and reporting.

Pulmonary function following early thoracic fusion in non-neuromuscular scoliosis.

BACKGROUND: While early spinal fusion may halt progressive deformity in young children with scoliosis, it does not facilitate lung growth and, in certain children, it can result in thoracic insufficiency syndrome. The purpose of this study was to determine pulmonary function at intermediate-term follow-up in patients with scoliosis who underwent thoracic fusion before the age of nine years. METHODS: Patients who had thoracic spine fusions before the age of nine years with a minimum five-year follow-up underwent pulmonary function testing. Forced vital capacity, forced expiratory volume in one second, and maximum inspiratory pressure were measured and compared with age-matched normal values. Patients with neuromuscular disease, skeletal dysplasias, or preexisting pulmonary disease were excluded, while those with rib malformations were included. The relationships between forced vital capacity and age at the time of surgery, length of follow-up, extent of the fusion, proximal level of the fusion, and revision surgery were studied. RESULTS: Twenty-eight patients underwent evaluation. Twenty patients had congenital scoliosis, three had idiopathic scoliosis, three had scoliosis associated with neurofibromatosis, one had congenital kyphosis, and one had syndromic scoliosis. Seventeen patients had one spinal surgery, while eleven had additional procedures. The average age of the patients was 3.3 years at the time of surgery and 14.6 years at the time of follow-up. The average extent of the thoracic spine fused was 58.7%. The average forced vital capacity was 57.8% of age-matched normal values, and the average forced expiratory volume in one second was 54.7%. The forced vital capacity was <50% of normal in twelve of the twenty-eight patients, and two required respiratory support, implying that substantial restrictive lung disease was present. With the numbers studied, no significant correlation could be detected between the age at the time of fusion or the length of follow-up and pulmonary function. The extent of the spine fused correlated with the forced vital capacity (p = 0.01, r = -0.46). Fusions in the proximal aspect of the spine were found to be associated with diminished pulmonary function as eight of twelve patients with a proximal fusion level of T1 or T2 had a forced vital capacity of <50%, but only four of sixteen patients with a fusion beginning caudad to T2 had a forced vital capacity of <50% (p = 0.0004, r = 0.62). CONCLUSIONS: Patients with proximal thoracic deformity who require fusion of more than four segments, especially those with rib anomalies, are at the highest risk for the development of restrictive pulmonary disease. Pulmonary function tests should be performed for all patients who have an early fusion. The pursuit of alternative procedures to treat early spinal deformity is merited.

Using propensity scoring to estimate program-related subgroup impacts in experimental program evaluations.

This article discusses the use of propensity scoring in experimental program evaluations to estimate impacts for subgroups defined by program features and participants' program experiences. The authors discuss estimation issues and provide specification tests. They also discuss the use of an overlooked data collection design--obtaining predictions that program intake staff make about applicants' likely program assignments and experiences--that could improve the quality of matched comparison samples. They demonstrate the effectiveness of this approach in producing credible subgroup findings using data from a large-scale experimental evaluation of Job Corps, the nation's largest federal education and training program for disadvantaged youths.

The effectiveness of early head start for 3-year-old children and their parents: lessons for policy and programs.

Early Head Start, a federal program begun in 1995 for low-income pregnant women and families with infants and toddlers, was evaluated through a randomized trial of 3,001 families in 17 programs. Interviews with primary caregivers, child assessments, and observations of parent-child interactions were completed when children were 3 years old. Caregivers were diverse in race-ethnicity, language, and other characteristics. Regression-adjusted impact analyses showed that 3-year-old program children performed better than did control children in cognitive and language development, displayed higher emotional engagement of the parent and sustained attention with play objects, and were lower in aggressive behavior. Compared with controls, Early Head Start parents were more emotionally supportive, provided more language and learning stimulation, read to their children more, and spanked less. The strongest and most numerous impacts were for programs that offered a mix of home-visiting and center-based services and that fully implemented the performance standards early.