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M94A3066.TXT
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1994-10-25
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Document 3066
DOCN M94A3066
TI A community-based study of the reliability of absolute CD4 lymphocyte
counts in HIV infected subjects.
DT 9412
AU Jimmerson C; Bockmon K; Harrison J; Houston Clinical Research Network,
TX 77006.
SO Int Conf AIDS. 1994 Aug 7-12;10(1):161 (abstract no. PB0070). Unique
Identifier : AIDSLINE ICA10/94369509
AB OBJECTIVES: CD4 cell counts are commonly used as surrogate markers. High
variability within these markers could limit their usefulness as a tool
for making treatment decisions. The variability of CD4 counts and
percentages performed by commercial laboratories was investigated.
METHODS: Three nationwide, contract laboratories were shipped blinded
samples from HIV-infected subjects (N = 52; CD4 > 100 and < 900). Two
samples per patient per laboratory were drawn and shipped concurrently.
Fixed effects, repeated measures ANOVA, and generalizability theory were
used to quantify sources of variation associated with results. RESULTS:
Absolute CD4 Lymphocyte Counts--Fourteen percent of the variance across
laboratories was associated with various sources of error rather than
differences among patients. The standard error of measurement for CD4
counts was approximately 70 cells/mm3. ANOVA indicated a significant (p
< .001) laboratory effect. The difference between samples was
significant (p < .02) within one of the laboratories and was often
clinically significant within all three laboratories. The overall
generalizability coefficient was .88 for a single sample from a single
laboratory. CD4 lymphocyte counts were not generalizable across
laboratories and thus not reliable for clinical decision making. CD4
Percentages--Five percent of the variance was associated with error. The
standard error was approximately 2%. A significant laboratory effect was
also observed (p < .001), and a difference (p < .01) between samples was
also found for the one laboratory noted above. The generalizability
coefficient was .95. CD4 percentages were more generalizable than
absolute cell counts. Variances in CD4 percentages were rarely
clinically significant. CONCLUSIONS: Future research involving a larger
number of laboratories and more stringent quality control mandates are
indicated. CD4 percentages may be more reliable than absolute cell
counts.
DE Biological Markers Human HIV
Infections/CLASSIFICATION/DIAGNOSIS/*IMMUNOLOGY *Leukocyte Count
Predictive Value of Tests Reproducibility of Results T4
Lymphocytes/*IMMUNOLOGY MEETING ABSTRACT
SOURCE: National Library of Medicine. NOTICE: This material may be
protected by Copyright Law (Title 17, U.S.Code).