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Comparison of CD4 cell count by a simple enzyme-linked immunosorbent assay using the TRAx CD4 test kit and by flow
Insights
A new TRAx CD4 test offers a cost-effective and reproducible method for monitoring CD4 T-lymphocyte levels, crucial for managing HIV infection. This ELISA-based assay shows strong correlation with traditional flow cytometry methods.
Area of Science:
- Immunology
- Clinical Diagnostics
- Biotechnology
Background:
- CD4 T-lymphocyte monitoring is vital for immune status assessment, particularly in managing human immunodeficiency virus (HIV) infection.
- Current methods using flow cytometry and hematology require complex instrumentation, are costly, and face standardization challenges.
- The global rise in HIV necessitates more reproducible and affordable CD4 T-cell monitoring techniques.
Purpose of the Study:
- To define the relationship between total CD4 protein measured by the novel TRAx CD4 assay and absolute CD4 counts obtained by conventional methods.
- To validate the TRAx CD4 assay's performance and assess its potential as an alternative diagnostic tool.
Main Methods:
- A multisite clinical study utilized linear regression analysis to correlate TRAx CD4 protein levels (units/mL) with absolute CD4 counts (cells/µL).
- Data from 230 HIV-seronegative and 321 HIV-seropositive specimens were used for assay calibration.
- Validation involved a second set of specimens tested under controlled conditions to minimize specimen aging effects.
Main Results:
- The TRAx CD4 assay demonstrated strong correlations with flow cytometry and hematology methods, ranging from 0.87 to 0.95.
- Calibration of the TRAx assay in cells/µL was validated, showing good precision.
- Contributions from monocytes and soluble CD4 were found to be negligible, ensuring assay specificity.
Conclusions:
- The TRAx CD4 test, based on ELISA adaptation, provides a simple and promising alternative for CD4 T-cell enumeration.
- This method addresses the need for cost-effective and reproducible CD4 monitoring, especially in resource-limited settings.
- The assay's performance suggests it can reliably guide therapy in conditions like HIV infection.
Abstract:
Measurement of CD4 T-lymphocyte levels is clinically useful in monitoring immune status in a number of conditions, including human immunodeficiency virus (HIV) infection, in which the absolute CD4 count is used to guide therapy. The absolute CD4 count is obtained by multiplying the results of the leukocyte count and the differential with a hematology cell counter and the percentage of CD4+ T lymphocytes determined by flow cytometry. These techniques require expensive, complex instrumentation, and interlaboratory results are difficult to standardize and reproduce. The rapid growth of HIV infection worldwide has increased the need for more-reproducible and cost-effective methods for CD4 T-cell monitoring. The TRAx CD4 test kit is based on a novel adaptation of conventional enzyme-linked immunosorbent assay (ELISA) and permits the simple quantitation of total CD4 protein from whole-blood lysates. In this study, the relationship between total CD4 protein measured in units per milliliter (TRAx) and in cells per microliter (flow cytometry and hematology) was defined in a multisite clinical study using linear regression analysis. Data from 230 HIV-seronegative and 321 HIV-seropositive specimens were used to calibrate the TRAx assay recombinant CD4 standards and controls in equivalent CD4 T lymphocytes per microliter (cells per microliter). The calibration of the TRAx CD4 assay in cells per microliter was validated with a second group of specimens from 17 healthy volunteers and 20 HIV-seropositive patients which were collected and tested under strictly controlled conditions intended to minimize the effects of specimen aging on the results of the reference method. These data were also used to estimate the variability of absolute CD4 count by cytometric methods as well as the precision of the TRAx CD4 result after it was calibrated in cells per microliter. Overall, correlations between the two methods ranged from 0.87 to 0.95. Additional studies demonstrated that the contribution of CD4 protein from monocytes and any soluble CD4 in sera are negligible in the TRAx assay and do not significantly affect results. This new method represents a promising alternative to absolute CD4 T-cell enumeration by flow cytometry and hematology.
