Document 0526
 DOCN  M9550526
 TI    Age-related reference ranges: significance tests for models and
       confidence intervals for centiles.
 DT    9505
 AU    Wade AM; Ades AE; Department of Epidemiology and Biostatistics,
       Institute of Child; Health, London, U.K.
 SO    Stat Med. 1994 Nov 30;13(22):2359-67. Unique Identifier : AIDSLINE
       MED/95158746
 AB    A method of fitting age-related reference ranges using maximized
       likelihood is presented. The method is illustrated using CD4 counts of
       uninfected children born to HIV-1 infected women. The likelihood
       incorporates exponential functions to describe the Box-Cox
       transformation parameter that induces Normality and the mean and
       standard deviation of the transformed data, at all ages in the range.
       This guarantees that the centiles are asymptotic to notional adult
       values and avoids edge effects. Likelihood ratio tests were used to
       assess the significance of the model parameters, and profile likelihood
       confidence intervals were constructed around the fitted centiles. The
       asymptotes of the resulting CD4 reference range for the childhood
       dataset were compared with CD4 counts available from a group of
       uninfected adults. The proposed approach limits the need for arbitrary
       decisions about grouping of the data, degree of smoothing or choice of
       model.
 DE    Acquired Immunodeficiency Syndrome/TRANSMISSION  Adult  Age Factors
       Child  Child, Preschool  Comparative Study  *Confidence Intervals  CD4
       Lymphocyte Count  Female  Human  HIV-1  Infant  Infant, Newborn
       Likelihood Functions  Male  *Models, Statistical  Pregnancy  Pregnancy
       Complications, Infectious  *Reference Values  JOURNAL ARTICLE

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