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Very low birth weight hospital volume and mortality: an instrumental variables approach.

ABSTRACT: Previous studies of very low birth weight (VLBW) hospital volume effects on in-hospital mortality have used standard risk-adjusted models that only account for observable confounders but not for self-selection bias due to unobservable confounders.To assess the effects of hospital volume of VLBW infants on in-hospital mortality while explicitly accounting for unobservable confounders and self-selection bias using an instrumental variables (IV) model.The sample includes 4553 VLBW infants born in 63 hospitals in 2000-2004 in New Jersey. We use IV analysis with the differences between the patient's distances to the nearest low (<50 VLBW infants annually), moderate (51-100 infants annually), and high (>100 VLBW infants annually)-volume hospitals as instruments. We evaluate several volume measures and adjusted for observable infant and hospital characteristics.We find beneficial volume effects on survival that are significantly underestimated in classic risk-adjusted models, under which low and moderate volumes compared with high volumes increase mortality odds by 1.8 and 1.88 times, respectively (risk ratios of 1.4 and 1.5, respectively). However, using the IV approach, we find that low and moderate volumes increase mortality odds by 5.42 and 3.51 times, respectively (risk ratios of 2.76 and 2.21, respectively). These findings suggest unobservable confounders that increase the selection of infants at a greater mortality risk into higher-volume hospitals.Accounting for unobserved self-selection bias reveals large survival benefits from delivering and treating VLBW infants at high-volume hospitals. This supports policies regionalizing the delivery and care for pregnancies at risk for VLBW at high-volume hospitals.

SUBMITTER: Wehby GL

PROVIDER: S-EPMC3388172 | biostudies-literature | 2012 Aug

REPOSITORIES: biostudies-literature

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Very low birth weight hospital volume and mortality: an instrumental variables approach.

Wehby George L GL Ullrich Fred F Xie Yang Y

Medical care 20120801 8

<h4>Background</h4>Previous studies of very low birth weight (VLBW) hospital volume effects on in-hospital mortality have used standard risk-adjusted models that only account for observable confounders but not for self-selection bias due to unobservable confounders.<h4>Objective</h4>To assess the effects of hospital volume of VLBW infants on in-hospital mortality while explicitly accounting for unobservable confounders and self-selection bias using an instrumental variables (IV) model.<h4>Method ...[more]

PMID: 22437621

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Project description:BACKGROUND:Invasive fungal infection is an important cause of mortality and morbidity in very preterm and very low birth weight infants. Early diagnosis is difficult and treatment is often delayed. Systemically absorbed antifungal agents (usually azoles) are increasingly used as prophylaxis against invasive fungal infection in this population. OBJECTIVES:To assess the effect of prophylactic systemic antifungal therapy on mortality and morbidity in very preterm or very low birth weight infants. SEARCH METHODS:We used the standard search strategy of the Cochrane Neonatal Review Group. This included searches of the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2015, Issue 8), MEDLINE, EMBASE, and CINAHL (to May 2015), conference proceedings, and previous reviews. SELECTION CRITERIA:Randomised controlled trials or quasi-randomised controlled trials that compared the effect of prophylactic systemic antifungal therapy versus placebo or no drug or another antifungal agent or dose regimen in very low birth weight infants. DATA COLLECTION AND ANALYSIS:We extracted data using the standard methods of the Cochrane Neonatal Review Group, with separate evaluation of trial quality and data extraction by two review authors. MAIN RESULTS:We identified 15 eligible trials enrolling a total of 1690 infants. Ten trials (1371 infants) compared systemic antifungal prophylaxis versus placebo or no drug. These trials were generally of good methodological quality. Meta-analysis found a statistically significant reduction in the incidence of invasive fungal infection (typical risk ratio (RR) 0.43, 95% confidence interval (CI) 0.31 to 0.59; risk difference (RD) -0.09, 95% CI -0.12 to -0.06). The average incidence of invasive fungal infection in the control groups of the trials (16%) was much higher than that generally reported from large cohort studies. Meta-analysis did not find a statistically significant difference in the risk of death prior to hospital discharge (typical RR 0.79, 95% CI 0.61 to 1.02; typical RD -0.04, 95% CI -0.07 to 0.00). Very limited data on long-term neurodevelopmental outcomes were available. Three trials that compared systemic versus oral or topical non-absorbed antifungal prophylaxis did not detect any statistically significant effects on invasive fungal infection or mortality. Two trials that compared different dose regimens of prophylactic intravenous fluconazole did not detect any significant differences in infection rates or mortality. AUTHORS' CONCLUSIONS:Prophylactic systemic antifungal therapy reduces the incidence of invasive fungal infection in very preterm or very low birth weight infants. This finding should be interpreted and applied cautiously since the incidence of invasive fungal infection was very high in the control groups of many of the included trials. Meta-analysis does not demonstrate a statistically significant effect on mortality. There are currently only limited data on the long-term neurodevelopmental consequences for infants exposed to this intervention. In addition, there is a need for further data on the effect of the intervention on the emergence of organisms with antifungal resistance.

Project description:ImportanceThrombocytopenia and intraventricular hemorrhage (IVH) are common among very-low-birth-weight (VLBW) infants. Survey results suggest that US neonatologists frequently administer platelet transfusions to VLBW infants with mild to moderate thrombocytopenia.ObjectivesTo characterize platelet transfusion practices in US neonatal intensive care units (NICUs), to determine whether severity of illness influences platelet transfusion decisions, and to examine the association between platelet count (PCT) and the risk for IVH in the first 7 days of life.Design, setting, and participantsThis multicenter, retrospective cohort study included 972 VLBW infants treated in 6 US NICUs, with admission dates from January 1, 2006, to December 31, 2007. Data were collected from all infants until NICU discharge or death (last day of data collected, December 4, 2008). Data were entered into the central database, cleaned, and analyzed from May 1, 2009, to February 11, 2016.InterventionPlatelet transfusion.Main outcomes and measuresNumber of platelet transfusions and incidence of IVH.ResultsAmong the 972 VLBW infants (520 [53.5%] male; mean [SD] gestational age, 28.2 [2.9] weeks), 231 received 1002 platelet transfusions (mean [SD], 4.3 [6.0] per infant; range, 1-63 per infant). The pretransfusion PCT was at least 50 000/μL for 653 of 998 transfusions (65.4%) with this information. Two hundred eighty-one transfusions (28.0%) were given during the first 7 days of life. During that period, platelet transfusions were given on 35 of 53 days (66.0%) when the patient had a PCT less than 50 000/μL and on 203 of 436 days (46.6%) when the patient had a PCT of 50 000/μL to 99 000/μL. At least 1 marker of severe illness was present on 198 of 212 patient-days (93.4%) with thrombocytopenia (PCT, <100 000/μL) when a platelet transfusion was given compared with 113 of 190 patient-days (59.5%) with thrombocytopenia when no platelet transfusion was given. Thrombocytopenia was a risk factor for intraventricular hemorrhage during the first 7 days of life (hazard ratio, 2.17; 95% CI, 1.53-3.08; P < .001). However, no correlation was found between severity of thrombocytopenia and risk for IVH. After controlling for significant clinical factors and thrombocytopenia, platelet transfusions did not have a significant effect on the incidence of IVH (hazard ratio, 0.92; 95% CI, 0.49-1.73; P = .80).Conclusions and relevanceA large proportion of platelet transfusions were given to VLBW infants with PCT greater than 50 000/μL. Severity of illness influenced transfusion decisions. However, the severity of thrombocytopenia did not correlate with the risk for IVH, and platelet transfusions did not reduce this risk.

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Very low birth weight hospital volume and mortality: an instrumental variables approach.

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Very low birth weight hospital volume and mortality: an instrumental variables approach.

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