As WHO recommends TB screening for all PLHIV before the initiation of ART [18] and haematological profile gives a snapshot of the body’s functionality, we questioned the possibility of using haematological parameters for this purpose. In order to identify differences in various haematological parameters and their ability to distinguish between individuals with PTB, PLHIV and HIV-TB coinfection from healthy controls, we analysed the haematological. Since the sensitivity of sputum microscopy falls within 24-61% [19] in PLHIV population, we ventured in with this novel approach of using the hemogram analysis which is a routine test done during any hospital visit, both in the outpatient and inpatient departments in order to evaluate its usefulness not only in TB diagnosis in the immunocompromised but also treaded one step ahead to see if it could distinguish the sub-groups as well. Haematology, if proven to be a good diagnostic/ screening tool may aid in early detection of HIV-TB coinfection, which will greatly benefit the society. Variations in haematological profile is a common phenomenon during any infection/ disease [20]. These changes are well documented across different infectious diseases including TB [21] and HIV [22].
As expected, the haematological parameters in healthy controls differed from the rest of three study groups. Of particular interest, as reported earlier [23, 24] we observed increased prevalence of anaemia among PTB participants and the prevalence of anaemia was further exacerbated by the HIV coinfection. This emphasises the fact that anaemia seen in PTB is due to the chest inflammatory conditions and not nutritional anaemia always. Thus, there is a possibility that control of PTB can reverse the anaemia status. This observation also reinforces the fact that special care should be given to TB and HIV-TB people with respect to redeeming their haemoglobin status to normal values for a successful recovery. Similarly, the increased prevalence of neutrophilia and lymphocytopenia in those with HIV-TB coinfection as compared to HIV infection alone, raises our opinion that these cells not only in their functions, but also in their numbers respond uniquely to infections.
In recent times, rather than the hematological analytes by themselves, their ratios have gained importance in various diagnoses. NLR has gained prominence as a prognostic/ diagnostic marker for cardiovascular and inflammatory diseases, coronavirus disease and several types of cancer [25-28] as well as respiratory disease like pneumonia and different forms of TB [29, 30]. Analogous to the above reports, we also found that NLR has great potential to serve as a screening tool to aid in TB diagnosis with a sensitivity of 87%. In addition to NLR, our analysis confirms the fact that MLR can be considered as a crucial biomarker to identify TB in adults (31).
Even though most of the parameters analysed were statistically different between the study groups, their diagnosing accuracy in differentiating between the groups was not satisfactory. Area under the curve was inadequate to rank them as good diagnostic markers as per the WHO’s, TPP for a diagnostic biomarker for tuberculosis with or without HIV. However, lymphocyte numbers (Table 3) had the greatest discriminative power compared to all other tested haematological parameters, in distinguishing TB from the healthy group. We did a combinatorial analysis of haematological parameters to check their diagnostic ability in differentiating between the four groups. By this method we report two different three signature panels, one for differentiating TB from healthy group and one for differentiating HIV-TB from PLHIV.
Even though it is widely agreed that these parameters are shown to be influenced during co-infections like PTB and HIV [12, 13] to our knowledge, no study has documented the use of these parameters as a screening criteria in the dually infected. With our observations presented here we provide small leads towards using haematological parameters as screening tools for HIV-TB coinfection among PLHIV group, in a low resource setting. Even though our data are from well characterized dataset, interpretation of haematological data should be made keeping in mind, underlying confounding factors like intake of drugs, diabetes, age and so forth. Also, the range identified here for the biosignatures cannot be generalized for diverse population across the globe. Further validation using multi-centric and multi-national cohorts will add strength to our investigations. Additional biomarkers like C- reactive protein might be added in the future studies, which is a limitation of our analysis. Presumptive TB cases identified by these signatures, may be subjected to further confirmatory tests like Xpert, culture and chest x-ray which will help in early diagnosis of TB among HIV positive individuals and help in rapid ATT initiation among this vulnerable population.