author_facet Newman, Thomas B.
Vittinghoff, Eric
McCulloch, Charles E.
Newman, Thomas B.
Vittinghoff, Eric
McCulloch, Charles E.
author Newman, Thomas B.
Vittinghoff, Eric
McCulloch, Charles E.
spellingShingle Newman, Thomas B.
Vittinghoff, Eric
McCulloch, Charles E.
Medical Decision Making
Efficacy of Phototherapy for Newborns with Hyperbilirubinemia : A Cautionary Example of an Instrumental Variable Analysis
Health Policy
author_sort newman, thomas b.
spelling Newman, Thomas B. Vittinghoff, Eric McCulloch, Charles E. 0272-989X 1552-681X SAGE Publications Health Policy http://dx.doi.org/10.1177/0272989x11416512 <jats:p>Background. Use of instrumental variables is gaining popularity as a method of controlling for confounding by indication in observational studies of treatments. Objectives. To illustrate how unmeasured instrument-level treatment substitution can distort effect size estimates using as an example an instrumental variable analysis of phototherapy for neonatal jaundice. Design. Retrospective cohort study. Setting. Northern California Kaiser Permanente Hospitals. Patients. The authors studied 20,731 newborns ≥2000 g and ≥35 weeks’ gestation born 1995–2004 with a “qualifying” total serum bilirubin (TSB) level within 3 mg/dL of the 2004 American Academy of Pediatrics (AAP) phototherapy threshold who did not have a positive direct antiglobulin test. Measurements. The intervention was inpatient phototherapy within 8 hours of the qualifying TSB. The outcome was a TSB level exceeding the AAP exchange transfusion threshold &lt;48 hours from the qualifying TSB. The instrumental variable was a measure of the frequency of phototherapy use at the newborn’s birth hospital. The unmeasured substituted treatment was supplementation with infant formula, assessed by chart review in a sample from the same cohort. Results. In total, 128 infants (0.62%) exceeded the exchange transfusion threshold. Logistic and propensity analyses yielded crude odds ratios of ~0.5 for phototherapy efficacy, decreasing to ~0.2 with control for confounding by indication. Instrumental variable analyses suggested much greater phototherapy efficacy (e.g., odds ratios of 0.02–0.05). However, chart reviews revealed greater use of infant formula (which also lowers bilirubin levels) in hospitals that used more phototherapy ( r = 0.56; P = 0.02), an association not present at the individual level ( r = 0.13). Conclusions. Instrumental variable analyses may provide biased estimates of treatment efficacy if there are cointerventions or confounders associated with treatment at the level of the instrument, although even when these associations may not exist in individuals.</jats:p> A Cautionary Example of an Instrumental Variable Analysis Efficacy of Phototherapy for Newborns with Hyperbilirubinemia : A Cautionary Example of an Instrumental Variable Analysis Medical Decision Making
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title_sub A Cautionary Example of an Instrumental Variable Analysis
title Efficacy of Phototherapy for Newborns with Hyperbilirubinemia : A Cautionary Example of an Instrumental Variable Analysis
title_unstemmed Efficacy of Phototherapy for Newborns with Hyperbilirubinemia : A Cautionary Example of an Instrumental Variable Analysis
title_full Efficacy of Phototherapy for Newborns with Hyperbilirubinemia : A Cautionary Example of an Instrumental Variable Analysis
title_fullStr Efficacy of Phototherapy for Newborns with Hyperbilirubinemia : A Cautionary Example of an Instrumental Variable Analysis
title_full_unstemmed Efficacy of Phototherapy for Newborns with Hyperbilirubinemia : A Cautionary Example of an Instrumental Variable Analysis
title_short Efficacy of Phototherapy for Newborns with Hyperbilirubinemia : A Cautionary Example of an Instrumental Variable Analysis
title_sort efficacy of phototherapy for newborns with hyperbilirubinemia : a cautionary example of an instrumental variable analysis
topic Health Policy
url http://dx.doi.org/10.1177/0272989x11416512
publishDate 2012
physical 83-92
description <jats:p>Background. Use of instrumental variables is gaining popularity as a method of controlling for confounding by indication in observational studies of treatments. Objectives. To illustrate how unmeasured instrument-level treatment substitution can distort effect size estimates using as an example an instrumental variable analysis of phototherapy for neonatal jaundice. Design. Retrospective cohort study. Setting. Northern California Kaiser Permanente Hospitals. Patients. The authors studied 20,731 newborns ≥2000 g and ≥35 weeks’ gestation born 1995–2004 with a “qualifying” total serum bilirubin (TSB) level within 3 mg/dL of the 2004 American Academy of Pediatrics (AAP) phototherapy threshold who did not have a positive direct antiglobulin test. Measurements. The intervention was inpatient phototherapy within 8 hours of the qualifying TSB. The outcome was a TSB level exceeding the AAP exchange transfusion threshold &lt;48 hours from the qualifying TSB. The instrumental variable was a measure of the frequency of phototherapy use at the newborn’s birth hospital. The unmeasured substituted treatment was supplementation with infant formula, assessed by chart review in a sample from the same cohort. Results. In total, 128 infants (0.62%) exceeded the exchange transfusion threshold. Logistic and propensity analyses yielded crude odds ratios of ~0.5 for phototherapy efficacy, decreasing to ~0.2 with control for confounding by indication. Instrumental variable analyses suggested much greater phototherapy efficacy (e.g., odds ratios of 0.02–0.05). However, chart reviews revealed greater use of infant formula (which also lowers bilirubin levels) in hospitals that used more phototherapy ( r = 0.56; P = 0.02), an association not present at the individual level ( r = 0.13). Conclusions. Instrumental variable analyses may provide biased estimates of treatment efficacy if there are cointerventions or confounders associated with treatment at the level of the instrument, although even when these associations may not exist in individuals.</jats:p>
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author_sort newman, thomas b.
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description <jats:p>Background. Use of instrumental variables is gaining popularity as a method of controlling for confounding by indication in observational studies of treatments. Objectives. To illustrate how unmeasured instrument-level treatment substitution can distort effect size estimates using as an example an instrumental variable analysis of phototherapy for neonatal jaundice. Design. Retrospective cohort study. Setting. Northern California Kaiser Permanente Hospitals. Patients. The authors studied 20,731 newborns ≥2000 g and ≥35 weeks’ gestation born 1995–2004 with a “qualifying” total serum bilirubin (TSB) level within 3 mg/dL of the 2004 American Academy of Pediatrics (AAP) phototherapy threshold who did not have a positive direct antiglobulin test. Measurements. The intervention was inpatient phototherapy within 8 hours of the qualifying TSB. The outcome was a TSB level exceeding the AAP exchange transfusion threshold &lt;48 hours from the qualifying TSB. The instrumental variable was a measure of the frequency of phototherapy use at the newborn’s birth hospital. The unmeasured substituted treatment was supplementation with infant formula, assessed by chart review in a sample from the same cohort. Results. In total, 128 infants (0.62%) exceeded the exchange transfusion threshold. Logistic and propensity analyses yielded crude odds ratios of ~0.5 for phototherapy efficacy, decreasing to ~0.2 with control for confounding by indication. Instrumental variable analyses suggested much greater phototherapy efficacy (e.g., odds ratios of 0.02–0.05). However, chart reviews revealed greater use of infant formula (which also lowers bilirubin levels) in hospitals that used more phototherapy ( r = 0.56; P = 0.02), an association not present at the individual level ( r = 0.13). Conclusions. Instrumental variable analyses may provide biased estimates of treatment efficacy if there are cointerventions or confounders associated with treatment at the level of the instrument, although even when these associations may not exist in individuals.</jats:p>
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spelling Newman, Thomas B. Vittinghoff, Eric McCulloch, Charles E. 0272-989X 1552-681X SAGE Publications Health Policy http://dx.doi.org/10.1177/0272989x11416512 <jats:p>Background. Use of instrumental variables is gaining popularity as a method of controlling for confounding by indication in observational studies of treatments. Objectives. To illustrate how unmeasured instrument-level treatment substitution can distort effect size estimates using as an example an instrumental variable analysis of phototherapy for neonatal jaundice. Design. Retrospective cohort study. Setting. Northern California Kaiser Permanente Hospitals. Patients. The authors studied 20,731 newborns ≥2000 g and ≥35 weeks’ gestation born 1995–2004 with a “qualifying” total serum bilirubin (TSB) level within 3 mg/dL of the 2004 American Academy of Pediatrics (AAP) phototherapy threshold who did not have a positive direct antiglobulin test. Measurements. The intervention was inpatient phototherapy within 8 hours of the qualifying TSB. The outcome was a TSB level exceeding the AAP exchange transfusion threshold &lt;48 hours from the qualifying TSB. The instrumental variable was a measure of the frequency of phototherapy use at the newborn’s birth hospital. The unmeasured substituted treatment was supplementation with infant formula, assessed by chart review in a sample from the same cohort. Results. In total, 128 infants (0.62%) exceeded the exchange transfusion threshold. Logistic and propensity analyses yielded crude odds ratios of ~0.5 for phototherapy efficacy, decreasing to ~0.2 with control for confounding by indication. Instrumental variable analyses suggested much greater phototherapy efficacy (e.g., odds ratios of 0.02–0.05). However, chart reviews revealed greater use of infant formula (which also lowers bilirubin levels) in hospitals that used more phototherapy ( r = 0.56; P = 0.02), an association not present at the individual level ( r = 0.13). Conclusions. Instrumental variable analyses may provide biased estimates of treatment efficacy if there are cointerventions or confounders associated with treatment at the level of the instrument, although even when these associations may not exist in individuals.</jats:p> A Cautionary Example of an Instrumental Variable Analysis Efficacy of Phototherapy for Newborns with Hyperbilirubinemia : A Cautionary Example of an Instrumental Variable Analysis Medical Decision Making
spellingShingle Newman, Thomas B., Vittinghoff, Eric, McCulloch, Charles E., Medical Decision Making, Efficacy of Phototherapy for Newborns with Hyperbilirubinemia : A Cautionary Example of an Instrumental Variable Analysis, Health Policy
title Efficacy of Phototherapy for Newborns with Hyperbilirubinemia : A Cautionary Example of an Instrumental Variable Analysis
title_full Efficacy of Phototherapy for Newborns with Hyperbilirubinemia : A Cautionary Example of an Instrumental Variable Analysis
title_fullStr Efficacy of Phototherapy for Newborns with Hyperbilirubinemia : A Cautionary Example of an Instrumental Variable Analysis
title_full_unstemmed Efficacy of Phototherapy for Newborns with Hyperbilirubinemia : A Cautionary Example of an Instrumental Variable Analysis
title_short Efficacy of Phototherapy for Newborns with Hyperbilirubinemia : A Cautionary Example of an Instrumental Variable Analysis
title_sort efficacy of phototherapy for newborns with hyperbilirubinemia : a cautionary example of an instrumental variable analysis
title_sub A Cautionary Example of an Instrumental Variable Analysis
title_unstemmed Efficacy of Phototherapy for Newborns with Hyperbilirubinemia : A Cautionary Example of an Instrumental Variable Analysis
topic Health Policy
url http://dx.doi.org/10.1177/0272989x11416512