DISCUSSION
This was a case of TBP diagnosed by ADA, treated successfully with clinical and radiological improvement. The pointers to diagnosis were duration of symptoms, constitutional symptoms, pleuritic chest pain, age of the patient (Porcel, 2009) and presence of pleural effusion. Another pointer was cytological finding of chronic lymphocytic pleuritis (Cohen and Light, 2015). These features are key in the diagnosis of TBP and any laboratory finding must be interpreted in the context of the clinical picture of the patient (Trajman et al. , 2008) (Wang et al. , 2015).
ADA an enzyme produced by T-helper type1(TH-1) lymphocytes, involved in purine metabolism is significantly raised in patients with TBP(Aggarwalet al. , 2019).Other disease states (such as malignant lymphomas, other malignant effusions, autoimmune diseases, empyema, para-pneumonic effusions) can cause elevated ADA levels (Shimoda et al. , 2022) (LIGHT, 2010) (Liang et al. , 2008) (Valdes et al. , 1996). However, in a longitudinal comparative study by Shimoda et al.,(2022) ADA levels were highest in TBP and of all causes of raised ADA, TBP was the most common cause (Shimoda et al. , 2022).
ADA test is very resourceful in the diagnosis of TB due to the fact that most “preferred” microbiological methods for diagnosis of TBP are limited by the paucibacillary nature of the pleural fluid (Cohen and Light, 2015) and it being mostly a hypersensitivity reaction (Morné J. Vorster, 2015). In low resource settings with scarcity of thoracoscopy/pleuroscopy services, pleural biopsies and histology are rarely done. The latter has demonstrated close to 100% sensitivity of the thoracoscopically obtained biopsies for histology and AFB stain (Diacon et al. , 2003) compared to 10% for pleural fluid AFB stain, about 45% for fluid MTB culture, and 38 to 75% for fluid Xpert ultra PCR (Lo Cascio et al. , 2021). The sensitivity of Abrams needle biopsies for histology and culture is estimated between 40 to 70% (Lo Cascio et al. , 2021).
No wonder, for our case pleural fluid ZN stain, Xpert ultra PCR, and culture were all negative for MTB. It is even more difficult to isolate the MTB in the fluid in HIV negative persons due to a robust immunity (lymphocytes, polymorphs and macrophage-monocyte system) which clear the organisms from the pleura (LUZZE, 2001).We didn’t do pleural biopsy due to lack of thoracoscopy/pleuroscopy and Abrams needle. Thus pleural fluid ADA test was instrumental in the diagnosis of TBP putting in context the clinical presentation of the patient and chronic lymphocytosis on fluid cytology. No comparison case studies/reports have been published in Uganda. Other causes of a raised ADA notwithstanding, the diagnostic accuracy, sensitivity and specificity of pleural fluid ADA test have been studied and recommended as sufficient (Nanyoshiet al. , 2022) (Lo Cascio et al. , 2021) (Hooper, Lee and Maskell, 2010) (Liang et al. , 2008) (LIGHT, 2010) (Diaconet al. , 2003).
Conclusion and recommendation : As has been shown in this case study and discussion plus previous literature, pleural fluid ADA test should be seriously considered and is highly recommended in the diagnostic pathway of TBP putting the clinical presentation and fluid lymphocytosis at the fore front. More so, in resource limited settings with no thoracoscopy/pleuroscopy and no equipment for closed pleural biopsy. This solves the TBP diagnostic delay, reducing the risk for complications and mortality.
CONFLICT OF INTEREST STATEMENT: Authors have no conflict of interest to declare.
ETHICS STATEMENT: All information displayed in this report was obtained as part of routine patient care. No ethical approval was required.
CONSENT STATEMENT: Written informed consent was obtained from the patient to publish this report in accordance with the journal’s patient consent policy.
DATA AVAILABILITY STATEMENT: The data that support the findings of this study are available from the corresponding author upon reasonable request.