Quality control of the total lymphocyte count parameter obtained from routine hacmatology analyzers, and its relevance in HIV management

Abstract

Lymphocyte subsJ/CD4 THelper cell enumeration in HIV care and treatment in resource constrained settings can be difficult to ascertain as a result of the lack of the necessary instrumentation, capacity and infrastructure. However, it is imperative to gain such information for patient monitoring in HIV. The Total Lymphocyte Count (TLC) is useful as a surrogate marker for CD4 count as recommended by the World Health Organisation (WHO) and to calculate CD4 % for paediatric use. This study therefore sets out to determine and compare the accuracy of the total lymphocyte counts obtained from three haematology analysers designated A. B and C. that are in regular use for routine haematological parameters at the main referral hospital in Barbados. West Indies. T he T LC of 263 HIV treatment naive individuals attending the HIV Reference Unit in Barbados were enumerated on the three haematology analysers. The 'lymphosum' (Sum of lymphocyte subsets: T-helper cell. T-cytotoxic cells. B lymphocytes and Natural killer cells) should be equal lo the TLC. and is derived by immunophcnotypic analysis on a 4-colour flowcytomeler. Machine C had the highest positive correlation between the T LC and the lymphosum with and R2 of 0.9031 compared to machine A with an R 2 values of 0.7119 and Machine B with R2 value s of 0.637. These results show that there can be dramatic inaccuracies when using routine haematology analysers for both routine use. as a surrogate marker of C D4 or for derivation of CD4 % in HIV management. It further demonstrates that all haematology analyzers require some form of Quality control. The possible lack of accuracy of the T LC by haematology analysers should be taken into consideration when following the recommendations of the W H O in resource poor settings or using it as a denominator for calculating CD4%.