Construction of a nomogram model based on multiple factors to differentiate cryptococcal meningitis from tuberculous meningitis in HIV-Infected patients

To develop and validate a nomogram model for differentiating cryptococcal meningitis (CM) from tuberculous meningitis (TBM) in HIV-infected patients, given the diagnostic challenges due to shared clinical manifestations and limitations of existing methods. A retrospective analysis extracted 207 HIV cases (112 CM, 95 TBM). Candidate predictor variables covering general information, blood biochemical, and cerebrospinal fluid(CSF) examination indicators were collected. Least absolute shrinkage and selection operator (LASSO) regression and ten-fold cross-validation identified key predictors, which were used to construct and validate the nomogram model. Model performance was evaluated by the area under the receiver operating characteristic (ROC) curve (AUC), calibration curves, and decision curve analysis (DCA). SHapley Additive exPlanations (SHAP) values were used to interpret the characteristics of the model's predictor variables. Five predictors (extracranial tuberculosis, extracranial fungi, erythrocyte sedimentation rate, albumin, and CSF pressure) were included in the final nomogram. The model achieved AUC of 0.830 (95% CI: 0.758-0.902) in the training set and 0.811 (95% CI: 0.719-0.904) in the testing set, with good calibration and clinical validity shown by calibration curves and DCA. The developed nomogram model effectively distinguishes CM from TBM in HIV-infected patients. It aids clinicians in diagnosis decisions.

Recent advances in microbiological and molecular biological detection techniques of tuberculous meningitis

Tuberculous meningitis (TBM) is the most common type of central nervous system tuberculosis (TB) and has the highest mortality and disability rate. Early diagnosis is key to improving the prognosis and survival rate of patients. However, laboratory diagnosis of TBM is often difficult due to its paucibacillary nature and sub optimal sensitivity of conventional microbiology and molecular tools which often fails to detect the pathogen. The gold standard for TBM diagnosis is the presence of MTB in the CSF. The recognised methods for the identification of MTB are acid-fast bacilli (AFB) detected under CSF smear microscopy, MTB cultured in CSF, and MTB detected by polymerase chain reaction (PCR). Currently, many studies consider that all diagnostic techniques for TBM are not perfect, and no single technique is considered simple, fast, cheap, and efficient. A definite diagnosis of TBM is still difficult in current clinical practice. In this review, we summarise the current state of microbiological and molecular biological diagnostics for TBM, the latest advances in research, and discuss the advantages of these techniques, as well as the issues and challenges faced in terms of diagnostic effectiveness, laboratory infrastructure, testing costs, and clinical expertise, for clinicians to select appropriate testing methods.

Diagnostic performance of real time PCR for the detection of Mycobacterium tuberculosis in cerebrospinal fluid samples

PURPOSE

We aimed this study to standardize real time - polymerase chain reaction (RT-PCR) for the detection of Mycobacterium tuberculosis (Mtb) in cerebrospinal fluid (CSF) samples and compare its diagnostic performance with GeneXpert (Xpert), Mycobacteria Growth Indicator Tube (MGIT) and Multiplex PCR (MPCR) for tuberculous meningitis (TBM).

METHODOLOGY

A total of 217 CSF samples were obtained from patients with suspected TBM during the study period between January 2019 and December 2021. The optimal cycle threshold (CT) of RT-PCR was determined by comparing different gene targets of Mtb (IS6110, 16SrRNA, HSP65 and Ag85B). Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) was determined for RT-PCR, Xpert, MGIT960 and MPCR. Diagnostic accuracy of these assays was compared by using clinical diagnosis as reference standard.

RESULTS

IS6110RT-PCR was found to be highly sensitive as compared to other gene targets. Sensitivities of IS6110RT-PCR, MPCR, Xpert and MGIT against a reference standard of definite, probable and possible TBM were 36.7%, 21.1%, 16.7% and 6.7%, respectively; specificities were 97.6%, 100%, 100% and 100%, respectively. Xpert, RT-PCR, MPCR and MGIT960 detected 6.91% (n = 15), 5.99% (n = 13), 5.99% (n = 13) and 2.76% (n = 6) of definite TBM, respectively. RT-PCR detected 6.45% (n = 14) and 2.76% (n = 6) of possible TBM and probable TBM, respectively and MPCR detected 1.38% (n = 3) of possible and probable TBM each.

CONCLUSION

IS6110RT-PCR is highly sensitive for primary screening of suspected TB cases, which may help clinicians to start appropriate patient's treatment with clinical suspicion of TBM.

Cerebrospinal fluid lactate as a predictive biomarker for tuberculous meningitis diagnosis

Objectives

The definitive diagnosis of tuberculous meningitis (TBM) is achieved by identifying Mycobacterium tuberculosis (MTb) in cerebrospinal fluid (CSF); however, diagnostic confirmation is difficult due to the inability of current tests for an effective diagnosis. Our objective was to retrospectively assess the characteristics of CSF lactate (CSF-LA) as an adjunct biomarker in the diagnosis of TBM.

Methods

608 CSF laboratory reports were assessed. Of these, 560 had clinically suspected TBM. These were classified as definite (n=36), probable (23), possible (278), or non-TBM (223) according to the international consensus TBM case definitions. An additional 48 CSF samples were negative controls with normal CSF.

Results

Against a reference standard of definite TBM, the cut-off value for CSF-LA was 4.0 mmol/L, the area under the ROC curve was 0.88 (95% CI, 0.82–0.94; p=0.0001), sensitivity was 69%, specificity 90%, negative predictive value 98%. These diagnostic parameters decreased when calculated against those of the other categories of TBM. CSF-LA exhibited high specificity, efficiency, negative predictive value, and clinical utility index in all the groups studied.

Conclusions

CSF-LA is a useful diagnostic marker to rule out TBM when associated with conventional microbiology tests, nucleic acid amplification assays, and clinical algorithms, particularly in endemic areas.

Real-time Polymerase Chain Reaction for Mycobacterium tuberculosis Meningitis is More Sensitive in Patients with HIV Co-Infection

BACKGROUND

Tuberculous meningitis (TbM) is the most severe complication of extra pulmonary tuberculosis (Tb). There is a higher frequency of positive cerebrospinal fluid (CSF) cultures for Mycobacterium tuberculosis (MTb) in samples from human immunodeficiency virus (HIV) co-infected patients than in those from HIV-negative patients. We hypothesized that real time PCR assays for MTb (MTb qPCR) using CSF would be more sensitive in HIV co-infected patients owing to a greater MTb burden. The present study aimed to verify the diagnostic performance of MTb qPCR in CSF of TbM patients who either were co-infected with HIV or were HIVnegative.

METHODS

A total of 334 consecutive participants with suspected TbM were divided into two groups: HIV co-infected and HIV-negative; each group was categorized into definite TbM, probable TbM, possible TbM, and TbM-negative subgroups based on clinical, laboratory and imaging data. We evaluated the diagnostic characteristics of MTb qPCR analysis to detect TbM in CSF by comparing the results to those obtained for definite TbM (i.e., positive MTb culture) and/or probable TbM in CSF, as gold standard.

RESULTS

The sensitivity of MTb qPCR in the definite and probable subgroups of the HIV coinfected participants (n = 14) was 35.7%, with a specificity of 93.8%, negative predictive value (NPV) of 94.4%, and negative clinical utility index (CUI-) of 0.89. Results of the HIV-negative group (n = 7) showed lower sensitivity (14.3%) and similar specificity, NPV, and CUI-.

CONCLUSION

The findings confirmed our hypothesis, despite the low sensitivity. MTb qPCR may significantly contribute to diagnosis when associated with clinical criteria and complementary examinations.

Central nervous system and spinal cord tuberculosis: Revisiting an important disease

Tuberculosis is a worldwide pandemic. Estimated that about 25% humans are colonized by Mycobacterium tuberculosis and about 1% are believed to develop the infection in the central nervous system (CNS-TB). Given the importance of this disease and its high levels of morbidity and mortality, it is imperative that every radiologist must be reminded of the most common findings of CNS-TB as there are several related differential diagnoses for this disease. The most common form CNS-TB is tuberculous meningitis (TBM), characterized mostly by basal meningitis, but infarction, hydrocephalus and tuberculomas could be present. Intracerebral tuberculosis is characterized by tuberculomas that can have different imaging features according to their stage. Vascular and spinal complications of tuberculosis are also reported. This review compiles the classic and unusual findings regarding CNS-TB together with new diagnostic scores in which neuroimaging have an important role.

Diagnostic characteristics of Xpert MTB/RIF assay for the diagnosis of tuberculous meningitis and rifampicin resistance in Southern Brazil

BACKGROUND

The timely diagnosis of tuberculous meningitis (TBM) is challenging. Molecular diagnostic tools are necessary for TBM, particularly in low- and middle-income countries.

OBJECTIVES

We aimed to calculate the diagnostics characteristics of Xpert MTB/RIF for the detection of Mycobacterium tuberculosis in the cerebrospinal fluid (CSF) and the frequency of rifampicin (RIF)-resistance in the CSF samples.

METHODS

A total of 313 consecutive CSF samples were studied and categorized into TBM definite, probable, possible, or not TBM cases based on the clinical, laboratory, and imaging data.

RESULTS

For the definite TBM cases (n=7), the sensitivity, specificity, efficiency, and positive likelihood ratio were 100, 97, 97, and 38%, respectively. However, for the TBM definite associated with the probable cases (n=24), the sensitivity decreased to 46%. All CSF samples that were Xpert MTB/RIF-positive were RIF susceptible.

CONCLUSION

Xpert MTB/RIF showed high discriminating value among the microbiology-proven TBM cases, although the values for the probable and possible TBM cases were reduced. Xpert MTB/RIF contributes significantly to the diagnosis of TBM, mainly when coupled with the conventional microbiological tests and clinical algorithms.

Central nervous system tuberculoma with miliary tuberculosis in the elderly

The aging phenomenon of tuberculosis (TB) patients is recognized all over the world, but no country is as prominent as Japan. Central nervous system (CNS) TB includes clinical entities: tuberculous meningitis, intracranial tuberculoma, and clinical features of CNS TB in the elderly may be atypical, non-specific, and confused with concomitant age-related diseases. Atypical clinical manifestations of TB in older persons can result in delay in diagnosis and initiation of treatment. A 91-year-old woman was brought to our emergency department after her family noted her altered mental status. Chest computed tomography confirmed miliary opacities. The cerebrospinal fluid (CSF) analysis showed elevated protein level, low glucose level, and a lymphocytic pleocytosis. Brain magnetic resonance imaging (MRI) showed multiple well‑defined enhancing lesions in the cerebral and cerebellar hemispheres and the pons, suggestive of tuberculomas. Smear, culture, and polymerase chain reaction (PCR) tests confirmed Mycobacterium tuberculosis in the sputum and aspirate. Based on the CSF and brain MRI findings and the sputum microbiology results indicating the presence of M. tuberculosis in the sputum and gastric aspirate, the patient was diagnosed with CNS tuberculoma. The onset of TB is mainly associated with decreased immunity; however, several other factors such as comorbidities, decreased activity, dysphagia, and malnutrition, which influence one another, also influence the development of TB in the elderly. Because the mortality rate of TB increases rapidly with age, reaching approximately 30 % among the elderly, early diagnosis is critical.