Flow cytometric CD4 enumeration of four different HIV-Infected blood samples at the cost of one monoclonal antibody reagent.

Background: Thefrequency and absolute number of CD4+ T-lymphocytes continue to be one of the major clinical markers for management of HIV/AIDS. The present standard dual-platform (DP) three-color and two-color PanLeucogating flow cytometric (FCM) methods for most developing countries are either expensive if manufacturers’ monoclonal antibody reagents are used or limited due to an insufficient supply of generic reagents. Clearly, more affordable FCM methods are needed. Objective: To develop a novel DP FCM method using biotin-streptavidin-fluorochrome labeling in combination with the two standard DP methods for 4 different white blood cells (WBC) using only one monoclonal antibody reagent. Methods: The percentage of CD4+ T-lymphocytes in 116 HIV-infected blood samples were determined using our new method. Results were compared with the two standard methods. Correlation and agreement of the pair method were determined using linear regression, Bland-Altman and percent similarity analysis. Results: Our study showed that percentage of CD4+ T-lymphocyte values obtained from the new method correlated highly with the standard three-color and the two-color methods (r2= 0.95 {n=52} and 0.97 {n=64}). The mean bias and percent similarity for the new method compared with the two standard methods were -0.53% (limit of agreement {LOA}:-5.22% to +4.16% with percent similarity of 99.28; and -0.22% with LOA of -3.42% to +2.98%, the percent similarity of 98.15, respectively. Conclusions: Our FCM method using biotin to label 4 different WBC samples followed by streptavidin staining is reliable for determination of CD4+ T-lymphocytes. Such an approach will significantly reduce the cost for monitoring HIV-infected patients in resource-limited settings.

External quality assessment program on CD4+ t-lymphocyte counts for persons with HIV/AIDS in Thailand: History and accomplishments.

A CD4 count External Quality Assessment (EQA) program is important for the clinical monitoring of persons infected with HIV/AIDS. The purpose of the present study was to evaluate the CD4 EQA performance program of the flow cytometer laboratories that perform routine CD4 counts for these patients in Thailand. Stabi-lized whole blood samples were sent to participating laboratories to determine the percentage and absolute counts of CD4+ T-lymphocytes using their routine procedures. The data were analyzed and reports sent to the participants within one month. Most participating laboratories produced results that were within two standard deviations (SD) of the mean, while the average inter-laboratory coefficients of variation were less than 8% for CD4+ T-lymphocytes. This program was found to improve the reliability of CD4+ T-lymphocyte determinations. This test is becoming in-creasingly important as Thailand and other Southeast Asian countries scale up their national programs that provide access to antiretroviral therapy for persons living with HIV/AIDS.

Red blood cell vesicles in thalassemia.

Vesicles are part of the red blood cells membrane which can be found in a small number in normal apoptotic process and increased in some diseases. In the present study, the authors measured the percentage of red blood cell vesicles in healthy subjects (n = 7), patients with alpha-thalassemia or Hemoglobin (Hb) H disease (n = 7), beta-thal/Hb E with nonsplenectomized (n = 5) and splenectomized (n = 7) before and after induction heated at 48.6 degrees C by using flow cytometry. It was found that the percentage of vesicles in every group were not statistically significantly different (p > 0.05) between pre and post incubation at 5 min. The percentage of vesicles of healthy subjects, beta-thal/Hb E nonsplenectomized patients and splenectomized patients were highest when induced by heating for 60 min. For patients with Hb H disease, the percentage of vesicles was maximum at 30 min when compared with healthy subjects, beta-thal/Hb E nonsplenectomized patients and splenectomized patients, respectively. In the present study, the authors report the significant increase of the percentage of vesicles in Hb H disease, beta-thal/Hb E nonsplenectomized and splenectomized after induction by heat when compared with healthy subjects. These findings may support the different pathology of the red blood cells found in alpha- and beta-thalassemia.

Low-cost CD4 enumeration in HIV-infected patients in Thailand.

In Thailand, over one million people have been infected with HIV since the beginning of the epidemic. This has created a great burden on the country's limited health care budget. Monitoring CD4+ T-lymphocytes is important to determine the success of any antiretroviral therapy as well as HIV vaccine trials. However, the high cost of CD4 counts makes monitoring of every HIV-infected patient impossible in Thailand. Therefore, the development of affordable strategies is necessary in order to allow more HIV infected persons to access CD4 testing to control the disease. The current standard methods for enumeration of CD4+ T-lymphocytes are performed on whole blood by flow cytometric immunophenotyping using the 6-tube 2-color and 3-tube 3-color panels recommended by the Centers for Diseases Control (CDC). In this study, percentage CD4+ T-lymphocyte values (from 142 HIV-seropositive patients and 26 anti-HIV negative adult blood donors) generated by the use of just 2 reagents (CD45/CD4) in a 1-tube 2-color panel employing side scatter/CD45 morphospectral gating were compared to those obtained by state of the art methods. We also compared the use of generic monoclonal antibody reagents with commercial reagents and found the results to be comparable with an overall correlation coefficient (r) of more than 0.95 for both CD4+ and CD8+ T-lymphocytes. Bland-Altman analysis of the mean CD4 values plotted against the difference in values between the generic reagents and the commercial reagents showed no bias. The 1-tube 2-color method using generic monoclonal antibody reagents potentially permits more affordable but reliable CD4 testing and therefore could increase access for more HIV-infected patients in resource-poor countries.