Page 317 - SAHCS HIVMed Journal Vol 20 No 1 2019

Page 6 of 7 Original Research

granuloma is associated with underlying mycobacterial and individual bone marrow aspirate and trephine specimens
infection rather than another cause. were not reanalysed; we were, therefore, unable to control
for any unidentified variables that may have influenced
Ziehl–Neelsen stain on bone marrow examination patient presentation. The subjectivity associated with the
Ziehl–Neelsen testing yielded positive results in 28% of cases. interpretation of the BMEs by the different assessors has to be
4
26
Van Schalkwyk et al. and Chosamata et al. found that 44% noted. In addition, the fact that the study cohort was obtained
and 65%, respectively, of patients with microbiological proven specifically from an ID ward in which the yield of tuberculosis
diagnosis of MTB on BME had concurrent positive ZN stains. and the HIV sero-prevalence is anticipated to be higher
This finding is far more than the 29% (16 of 55 cases) found in than that of a general medical ward having patients with
the current study. This may be accounted for by the greater both communicable and non-communicable diseases may
percentage of patients already on empiric tuberculosis influence how the study findings may be applied to primary
treatment in the current study, with 43.6% (17 of 39 cases) of or district hospital settings in SA.
those with positive MTB cultures and negative ZN stains
being on empiric treatment at the time of the study. Conclusion

Predictors of Mycobacterium tuberculosis on bone The findings in this study conclude that bone marrow aspirate
marrow examination and trephine examinations still provide utility as a diagnostic
tool even in the current South African setting of more
9
This study found a WCC ≤ 4 × 10 /L and CD4 cell count ≤ 50
3
cells/mm were predictors of a confirmed diagnosis of comprehensive rollout of ART as well as increased availability
mycobacterial infection on BME. A similar finding of a lower of novel diagnostic tests for MTB. This finding applies
CD4 count in those with positive mycobacterial findings on particularly to patients in an ID ward in whom non-invasive
BME was found in the 2015 study by Sedick et al., in which standard investigations for the presence of cytopenias on
27
the median CD4 cell count range amongst the different peripheral blood have been negative and the concern
methods of diagnosing mycobacterial infection on BME was of disseminated mycobacterial infection remains high.
between 7 cells/mm and 33 cells/mm . The statistical Performance of a bone marrow aspirate and trephine in these
3
3
significance of this finding was, however, not evaluated. circumstances, through aiding with diagnosis, allows initiation
and/or changes in patient treatment plans and by inference
Mycobacterium avium complex on bone marrow would most likely improve patient outcomes. The ongoing
examination advancements occurring in the field of molecular diagnostics
Four individuals in this study had MAC cultured on BME, as may in the future further revolutionise the efficacy and means
compared to 49 who had MTB cultured. This finding is in of diagnostic tests utilised in such patients. Although the
contrast to studies conducted in the developed world, which current study shows persistent diagnostic utility of BMEs, these
reflect a higher prevalence of MAC infection as compared to ongoing advancements such as introduction of geneXpert Ultra
MTB. 5,6,9,10,11,12,13 In the London study by Riley et al., MAC testing may reduce the need for BME in the future. Furthermore,
11
was the organism most commonly found on bone marrow similar studies should be carried out and the current study
culture (42 of 51 cases). The investigators also found that of would be a good marker to compare future studies against.
the patients in their study diagnosed with MAC, this was a
unique diagnosis in one third of the cases, which for them Our final recommendation would be to conduct the least
highlighted the usefulness of BME in aiding with MAC invasive investigations first. If no success is obtained in
diagnosis. The utility of BME in diagnosing MAC in the making a diagnosis, a BME is then recommended.
current study was difficult to comment on given the small Mycobacterial cultures on blood and bone marrow specimens
sample of patients who cultured MAC, namely 4 out of 55 should be performed together to allow for optimal yield.
positive bone marrow culture results. This finding may also Bone marrow trephine results should ideally be made
reflect a sampling bias as MAC is difficult to diagnose and is available to the clinician within 2 weeks of the performance
often only looked for on BME if the clinical suspicion exists. of the test. Unfortunately, this is often difficult in the resource-
Given the available literature, however, BME appears to be a limited public sector in SA. It is imperative in those patients
useful means to diagnose MAC in areas with higher disease who have been started on empiric TB therapy to follow up
prevalence. the results of these invasive investigations in order to confirm
the diagnosis and to exclude other unexpected diagnoses.
Potential limitations of the study Acknowledgements
There were a few potential limitations of this study. This was
a single centre study undertaken in a single unit and so the Competing interests
results may not be generalisable to other units or to other The authors have no conflict of interests.
hospitals in SA. Study patients were already in an ID ward
with clinically advanced HIV at the time of the study, this at Authors’ contributions
the outset would favour the presence of opportunistic
infections, particularly MTB. Bone marrow findings were N.B. assisted in conceptualising the study and writing the
obtained from the retrospective review of published reports protocol, performed the data collection and data analysis and

http://www.sajhivmed.org.za 310 Open Access