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

: Lylmphocyte subsets/CD4 T Helper 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 pacdiatric 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 haemnatological parameters at the main referral hospital in Barbados. West Indies. The TLC of 263 HIV treatment naive individuals attending the HIV Reference Unit in Barbados were enumnerated on the three haematology analysers. The lymphosumn (Sum of lymphocyte subsets: T-helper cell. T-cytotoxic cells. B lymphocytes and Natural killer cells) should be equal to the TLC. and is derived by immunophenotypic analysis on a 4-colour flowcytometer. Machine C had the highest positive correlation between the TLC and the lymphosumn with and R' of 0.9031 compared to machine A with an R values of 0.7119 and Machine B with R(2) values 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 CD4 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 TLC by haematology analysers should be taken into consideration when following the recommendations of the WHO in resource poor settings or using it as a denominator for calculating CD4%.