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M anagement of Neonatal Hyperbilirubinemia Methods of the AHRQ Evidence Report FDA Advisory Committee Meeting June 11, 2

M anagement of Neonatal Hyperbilirubinemia Methods of the AHRQ Evidence Report FDA Advisory Committee Meeting June 11, 2003. Joseph Lau, MD Tufts-New England Medical Center EPC. INVESTIGATORS Stanley Ip, MD Mei Chung, MPH Stephan Glicken, MD John Kulig, MD Rebecca O’Brien, MD

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M anagement of Neonatal Hyperbilirubinemia Methods of the AHRQ Evidence Report FDA Advisory Committee Meeting June 11, 2

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  1. Management of Neonatal HyperbilirubinemiaMethods of the AHRQ Evidence ReportFDA Advisory Committee MeetingJune 11, 2003 Joseph Lau, MD Tufts-New England Medical Center EPC

  2. INVESTIGATORS Stanley Ip, MD Mei Chung, MPH Stephan Glicken, MD John Kulig, MD Rebecca O’Brien, MD Robert Sege, MD, PhD Joseph Lau, MD

  3. Evidence report process • Rigorous, comprehensive syntheses and analyses of relevant scientific literature • Explicit and detailed documentation of methods, rationale, and assumptions • Scientific syntheses may include meta-analyses and cost analyses • Broad range of experts is included in the development process • Reports do NOT make clinical recommendations

  4. Systematic review process • Formulate well focused study questions • Establish evidence review protocol (inclusion and exclusion criteria) • Perform comprehensive literature search • Screen abstracts and full articles • Abstract data and perform critical appraisal • Perform analyses, summarize and interpret results

  5. Key questionsAssociation of neonatal hyperbilirubinemia with neurodevelopmental outcomes • What is the relationship between peak bilirubin levels and/or duration of hyperbilirubinemia and developmental outcome? • What is the evidence for effect modification of the results in question 1, by gestational age, hemolysis, serum albumin, and other factors?

  6. Key questions (cont.)Treatments for neonatal hyperbilirubinemia • What are the quantitative estimates of efficacy of treatment for: • reducing peak bilirubin levels (e.g., number-needed-to-treat (NNT) at 20 mg/dl to keep total serum bilirubin (TSB) from rising); • reducing the duration of hyperbilirubinemia (e.g., average number of hours by which time TSB greater than 20 mg/dl may be shortened by treatment); and • improving neurodevelopmental outcomes.

  7. Key questions (cont.)Diagnosis of neonatal hyperbilirubinemia • What is the efficacy of various strategies for predicting hyperbilirubinemia, including hour-specific bilirubin percentiles? • What is the accuracy of transcutaneous bilirubin measurements?

  8. Literature search • Medline and Premedline databases searched September 2001, yielding 4,325 citations • Consulted domain experts and reviewed bibliography of relevant review articles for potential additional studies • Supplemental search for case reports of kernicterus was also performed

  9. General inclusion criteria • English language human studies • Newborns between birth and one-month • Healthy, full-term infants •  34 weeks EGA or  2,500 grams •  10 subjects per arm (5 for Q1 and Q2) • Additional criteria were applied to specific question

  10. Literature search results • Total citations screened = 4,325 • Full articles retrieved = 663 • Studies included in report = 138* • Q1/Q2 = 37 + 28 kernicterus case reports • Q3 = 21 • Q4 = 10 • Q5 = 46 * Total of counts of individual questions exceeds 138 due to overlapping coverage

  11. Summarizing and grading of evidence

  12. Important parameters to sum up • Methodological quality (internal validity, design, conduct, and reporting of the study) • Applicability (generalizability, external validity, population, setting) • Study size (weight, precision) • Effect (results, associations, test performance)

  13. Methodological quality Refers to the design, conduct, and reporting of the clinical study. Because studies may be from a variety of types of design, the following three-level classification of study quality may be used to apply to each type of design. • Least potential bias (Grade A) • Susceptible to some bias, but not sufficient to invalidate the results (Grade B) • Significant bias that may invalidate the result (Grade C)

  14. Applicability Category 1: Sample is representative of the target population, or if results are definitely applicable to general population irrespective of study sample. Category 2: Sample is representative of a relevant sub-group of the target population. Category 3: Sample is representative of a narrow subgroup of patients only, and not well generalizable to other subgroups.

  15. Quantitative methods used in evidence report

  16. Question 3: NNT What are the quantitative estimates of efficacy of treatment for: reducing peak bilirubin levels (e.g., number-needed-to-treat (NNT) at 20 mg/dl to keep total serum bilirubin (TSB) from rising)?

  17. Hypothetical example of treating bilirubin at 15 mg/dl to prevent it from rising Risk Difference = 10/100 – 20/100 = -10/100 = -0.1 NNT = 1 / Risk Difference = 1/10 = 10

  18. Methods to assess agreement between two testing methods reported in studies • Correlation (r value) • Meta-analyses performed in evidence report when data available • Bland and Altman method (difference of results of two testing methods plotted against their mean value) • Preferred method

  19. Accuracy of BilicheckTMBhutani et al., Pediatrics 2000

  20. Limitations of correlation coefficient to assess agreement (hypothetical data - all have correlation coefficient of 1)

  21. Limitations of correlation coefficients in assessing agreement between two testing methods • Correlation coefficient provides a measure of the strength and directionality of the association, but NOT agreement • Correlation measures ignore bias • Correlation coefficient does not provide information as to clinical utility of diagnostic test • Correlation coefficient (r) is dependent on distribution of serum bilirubin • Measures relative rather than absolute agreement • High correlation coefficient is a necessary but not a sufficient condition to assess agreement

  22. Bland and Altman method • True value is unknown • Takes the average of the paired measurements as the best estimate • Plot for each pair of measurements, the difference in results between devices against the average results • Removes statistical artifact of plotting the difference against either of the measurement (built-in correlation) • The magnitude of bias can be estimated as well as the standard deviation of the differences

  23. Error distribution paired HPLC TSB and TcBBhutani et al., Pediatrics 2000

  24. Common methods to summarize diagnostic test performance • Combining sensitivity and specificity independently • Combining diagnostic odds ratios across studies • Summary ROC curve

  25. Summary ROC methodMoses LE, Shapiro D, Littenberg B. Combining independent studies of a diagnostic test into a summary ROC curve: Data-analytic approaches and some additional considerations. Stat Med 1993; 12:1293-1316. • Assumption: studies results differ because of different thresholds • Solution: fit a curve in the ROC space that best describes the data • Problem: sensitivity and specificity are correlated • Solution: regress the difference of the logits onto the sum of logits and transform back to ROC space

  26. ROC curve constructed from multiple test thresholds

  27. Examples of SROC curves and pooled sensitivity and specificity

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