Biomedical subjects

Lesley E Scott

Publications and source records attributed to Lesley E Scott.

3 recordsLinked to original sources

PubMed2003

Multiple method comparison: statistical model using percentage similarity.

BACKGROUND: Method comparison typically determines how well two methods agree. This is usually performed using the difference plot model, which measures absolute differences between two methods. This is often not applicable to data with wide ranges of absolute values. An alternative model is introduced that simplifies comparisons specifically for multiple methods compared to a gold standard. METHODS: The average between a new method and the gold standard is represented as a percentage of the gold standard. This is interpreted as a percentage similarity value and accommodates wide ranges of data. The representation of the percentage similarity values in a histogram format highlights the accuracy and precision of several compared methods to a gold standard. The calculation of a coefficient of variation further defines agreement between methods. RESULTS: Percentage similarity histograms of several new methods can be compared to a gold standard simultaneously, and the comparison easily visualized through use of a single 100% similarity reference line drawn common to all plots. CONCLUSION: This simple method of comparison would be particularly useful for multiple method comparison and is especially applicable for centers collating for external quality assessment or assurance programs to demonstrate differences in results between laboratories.

Biometry↗

PubMed2002

CD45-assisted PanLeucogating for accurate, cost-effective dual-platform CD4+ T-cell enumeration.

BACKGROUND: North American and European guidelines for dual-platform (DP) flow cytometry recommend absolute CD4 T-cell counts to be calculated from two parameters: the absolute lymphocyte counts obtained on a hematology analyzer and the percentages of CD4+ cells among lymphocytes (CD4%/lympho) obtained by flow cytometry. Nevertheless, the identification of lymphocytes is error-prone: a poor match between these common denominators in the two systems is the main source of inaccuracy. In contrast, total leucocyte counts (white cell counts [WCC]) and CD4% among the gated CD45+ leucocytes (CD4%/leuco) can be determined with greater accuracy. METHODS: We introduced "PanLeucogating," i.e., we used total leucocytes as the common denominator for improving the precision of DP absolute CD4 counting. Correlations and Bland-Altman tests were used for statistical analysis. RESULTS: First, 22 stabilized blood product samples were provided by U.K. National External Quality Assessment Scheme (NEQAS) and a higher accuracy and precision of CD4 counts were documented using PanLeucogating compared with lymphocyte gating. Next, 183 fresh and 112 fixed (TransFix) whole blood samples were used to compare DP methods and single-platform (SP) methodology, including both volumetric and bead-based techniques. A particularly high correlation and comparable precision of absolute CD4 counts were observed between the SP volumetric method and DP PanLeucogating (R(2) = 0.990; bias 6 +/- SD 17%). The SP volumetric method showed lower levels of agreement with the DP lymphocyte gating (R(2) = 0.758; bias 14 +/- SD 51%) and with the SP bead-based method (R(2) = 0.923; bias 4 +/-SD 31%). CONCLUSIONS: These observations show that DP leucocyte counts (WCC) should replace lymphocyte counts as the "common denominator" although CD4%/lympho values can, as an extra step, be also provided readily if requested. When coupled with quality control for WCC on hematology analyzers, the DP method with CD45 PanLeucogating represents a robust CD4 T-cell assay that is as accurate as the SP volumetric technique. This DP method uses only two, CD45 and CD4, antibody reagents and can be run on any pair of hematological analyzer plus flow cytometer.

CD4-Positive T-Lymphocytes↗

PubMed2002

CD38 expression on CD8(+) T cells as a prognostic marker in vertically HIV-infected pediatric patients.

Increased expression of CD38 on CD8(+) T cells is associated with activation of the immune system, progression of HIV disease, and death in adults. The prognostic significance of these cells in HIV-infected children, where the picture is complicated by age-related differences in CD38 expression, remains controversial. Measuring the unimodal expression of CD38 on CD8(+) T cells in adults and children by flow cytometry is best accomplished by quantitating the antigen on the cell surface. To our knowledge, this technique has not previously been reported in a pediatric population. Vertically HIV-infected children were age matched for mild (n = 26) and severe (n = 23) clinical disease. Eleven age-matched HIV-negative controls were included for comparison. Quantitation of CD38 on CD8(+) T cells was performed at baseline and 1 y later. The ages of the children in the three clinical groups did not differ significantly (p = 0.6004). HIV-infected children had significantly increased CD38 measurements in comparison with the HIV-negative controls (p = 0.0131), and the severe disease group tended to have higher measurements than the mild disease group. Increased CD38(+)CD8(+) T cells were significant predictors of death within the first year (p = 0.043). These findings support the view that increased CD38 expression on CD8(+) T cells has the same prognostic significance in pediatric as in adult HIV disease.

ADP-ribosyl Cyclase↗