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Helper T-lymphocyte count. TRAx CD4 test kit versus conventional flow cytometry
A J Saah1, C Spruill, D R Hoover
1Department of Epidemiology, Johns Hopkins School of Public Health, Baltimore, MD 21205, USA.
Insights
The TRAx enzyme-linked immunosorbent assay is an acceptable method for measuring helper T-lymphocyte counts. Recalibration is recommended for improved accuracy below 200 cells/µL.
Area of Science:
- Immunology
- Clinical Diagnostics
- Assay Development
Background:
- Helper T-lymphocyte (CD4+) counts are critical for monitoring immune status, particularly in HIV infection.
- Accurate enumeration of T-lymphocytes is essential for guiding therapeutic interventions.
- Novel diagnostic assays require rigorous validation against established methods.
Purpose of the Study:
- To evaluate the performance of a new enzyme-linked immunosorbent assay (ELISA) system, TRAx, for quantifying helper T-lymphocyte counts.
- To compare the results obtained from the TRAx ELISA with those from flow cytometry, a standard method.
Main Methods:
- A cohort of 111 human immunodeficiency virus-infected injection drug users was studied.
- Helper T-lymphocyte counts were determined using both flow cytometry and duplicate runs of the TRAx ELISA.
- Statistical analysis included correlation coefficients and cross-tabulation to assess agreement.
Main Results:
- The TRAx ELISA demonstrated high correlation with flow cytometry (r = .93 and .91).
- Agreement between TRAx and flow cytometry was substantial for counts >200 cells/µL (71-90%).
- Performance at counts ≤200 cells/µL showed variability (41-73% agreement).
Conclusions:
- The TRAx ELISA system is a viable option for helper T-lymphocyte measurement.
- Recalibration of the TRAx ELISA is necessary to enhance accuracy for low T-cell counts (<200 cells/µL).
- Further optimization may improve its utility in clinical settings with low lymphocyte counts.
Background:
We evaluated a newly developed enzyme-linked immunosorbent assay system for measuring helper T-lymphocyte count.
Methods:
Data from 111 human immunodeficiency virus-infected injection drug users in a cohort study were analyzed by flow cytometry and independent duplicate runs of the TRAx enzyme-linked immunosorbent assay.
Results:
The mean helper T-cell counts were 470, 480, and 506 per microliter by flow cytometry and TRAx runs 1 and 2, respectively. The correlation coefficients for TRAx runs 1 and 2 with the flow cytometry results as the dependent variable were .93 and .91, respectively. A cross-tabulation of the enzyme-linked immunosorbent assay helper T-lymphocyte counts with flow cytometry counts showed agreement of 71% and 76% when the flow count was between 201 and 500, and 88% and 90% when it was greater than 500 cells per microliter. In those samples with 200 or fewer helper T cells, agreement was 73% and 41% for each TRAx run.
Conclusions:
The TRAx enzyme-linked immunosorbent assay system is an acceptable method for measuring helper T-lymphocyte count, but should be recalibrated for better performance at helper T-cell counts below 200 per microliter.
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