Retrospective diagnosis of lymphatic tuberculosis in frozen samples using two genetic amplification methods, Xpert® MTB/RIF ULTRA and Abbott RealTime MTB Assay

Objectives

The main objective of the present study is to assess the sensitivity and specificity of a retrospective diagnostic of lymphatic tuberculosis (LTB), testing frozen samples using gene amplification PCR methods. The secondary objective was to compare the results of two different commercial tuberculosis gene amplification methods for this purpose.

Material and methods

We retrospectively studied 38 frozen samples, previously processed for mycobacterial culture between January 2014 and August 2019. The results of the previous cultures were: 21 samples positive for Mycobacterium tuberculosis complex (MTB) (5 being smear positive), 7 samples culture positive for Mycobacterium avium-intracellulare complex and 10 samples which were mycobacterial culture negative and discarded for LTB diagnosis, used as controls. The samples were processed using two gene amplification methods: Xpert® MTB/RIF Ultra (Cepheid) and Abbott RealTime MTB Assay (Abbott).

Results

Compared to initial culture results the sensitivity and specificity of Xpert® MTB/RIF Ultra were 57.1% and 100% and 52.3 % and 92.5%, respectively for the Abbott RealTime MTB assay. The differences were not statistically significant. In addition, there were no differences according to the period of freezing.

Conclusions

Gene amplification of frozen samples confirmed the diagnosis of lymphatic TB in almost 60% of cases, allowing retrospective diagnosis in initially non suspected cases. Both gene amplification techniques tested were equally useful.

Tocilizumab reduces the risk of ICU admission and mortality in patients with SARS-CoV-2 infection

Objectives

In some patients the immune response triggered by SARS-CoV-2 is unbalanced, presenting an acute respiratory distress syndrome which in many cases requires intensive care unit (ICU) admission. The limitation of ICU beds has been one of the major burdens in the management around the world; therefore, clinical strategies to avoid ICU admission are needed. We aimed to describe the influence of tocilizumab on the need of transfer to ICU or death in non-critically ill patients.

Material and methods

A retrospective study of 171 patients with SARS-CoV-2 infection that did not qualify as requiring transfer to ICU during the first 24h after admission to a conventional ward, were included. The criteria to receive tocilizumab was radiological impairment, oxygen demand or an increasing of inflammatory parameters, however, the ultimate decision was left to the attending physician judgement. The primary outcome was the need of ICU admission or death whichever came first.

Results

A total of 77 patients received tocilizumab and 94 did not. The tocilizumab group had less ICU admissions (10.3% vs. 27.6%, P=0.005) and need of invasive ventilation (0 vs 13.8%, P=0.001). In the multivariable analysis, tocilizumab remained as a protective variable (OR: 0.03, CI 95%: 0.007-0.1, P=0.0001) of ICU admission or death.

Conclusions

Tocilizumab in early stages of the inflammatory flare could reduce an important number of ICU admissions and mechanical ventilation. The mortality rate of 10.3% among patients receiving tocilizumab appears to be lower than other reports. This is a non-randomized study and the results should be interpreted with caution.