Tuberculous meningitis: does lowering the treatment threshold result in many more treated patients?

A novel diagnostic model for tuberculous meningitis using Bayesian latent class analysis

BACKGROUND

Diagnosis of tuberculous meningitis (TBM) is hampered by the lack of a gold standard. Current microbiological tests lack sensitivity and clinical diagnostic approaches are subjective. We therefore built a diagnostic model that can be used before microbiological test results are known.

METHODS

We included 659 individuals aged [Formula: see text] years with suspected brain infections from a prospective observational study conducted in Vietnam. We fitted a logistic regression diagnostic model for TBM status, with unknown values estimated via a latent class model on three mycobacterial tests: Ziehl-Neelsen smear, Mycobacterial culture, and GeneXpert. We additionally re-evaluated mycobacterial test performance, estimated individual mycobacillary burden, and quantified the reduction in TBM risk after confirmatory tests were negative. We also fitted a simplified model and developed a scoring table for early screening. All models were compared and validated internally.

RESULTS

Participants with HIV, miliary TB, long symptom duration, and high cerebrospinal fluid (CSF) lymphocyte count were more likely to have TBM. HIV and higher CSF protein were associated with higher mycobacillary burden. In the simplified model, HIV infection, clinical symptoms with long duration, and clinical or radiological evidence of extra-neural TB were associated with TBM At the cutpoints based on Youden's Index, the sensitivity and specificity in diagnosing TBM for our full and simplified models were 86.0% and 79.0%, and 88.0% and 75.0% respectively.

CONCLUSION

Our diagnostic model shows reliable performance and can be developed as a decision assistant for clinicians to detect patients at high risk of TBM. Diagnosis of tuberculous meningitis is hampered by the lack of gold standard. We developed a diagnostic model using latent class analysis, combining confirmatory test results and risk factors. Models were accurate, well-calibrated, and can support both clinical practice and research.

Clinical features of adult patients with a definite diagnosis of central nervous system tuberculosis in an endemic country: A 13-year retrospective review

Rationale

Objectives

Methods

Measurements and main results

Conclusions

Six months therapy for tuberculous meningitis

BACKGROUND

Tuberculous meningitis (TBM) is the main form of tuberculosis that affects the central nervous system and is associated with high rates of death and disability. Most international guidelines recommend longer antituberculous treatment (ATT) regimens for TBM than for pulmonary tuberculosis disease to prevent relapse. However, longer regimens are associated with poor adherence, which could contribute to increased relapse, development of drug resistance, and increased costs to patients and healthcare systems.

OBJECTIVES

To compare the effects of short-course (six months) regimens versus prolonged-course regimens for people with tuberculous meningitis (TBM).

SEARCH METHODS

We searched the following databases up to 31 March 2016: the Cochrane Infectious Diseases Group Specialized Register; the Cochrane Central Register of Controlled Trials (CENTRAL), published in the Cochrane Library; MEDLINE; EMBASE; LILACS; INDMED; and the South Asian Database of Controlled Clinical Trials. We searched the World Health Organization International Clinical Trials Registry Platform (WHO ICTRP) and ClinicalTrials.gov for ongoing trials. We also checked article reference lists and contacted researchers in the field.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) and prospective cohort studies of adults and children with TBM treated with antituberculous regimens that included rifampicin for six months or longer than six months. The primary outcome was relapse, and included studies required a minimum of six months follow-up after completion of treatment.

DATA COLLECTION AND ANALYSIS

Two review authors (SJ and HR) independently assessed the literature search results for eligibility, and performed data extraction and 'Risk of bias' assessments of the included studies. We contacted study authors for additional information when necessary. Most data came from single arm cohort studies without a direct comparison so we pooled the findings for each group of cohorts and presented them separately using a complete-case analysis. We assessed the quality of the evidence narratively, as using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach was inappropriate with no direct comparisons between short- and prolonged-course regimens.

MAIN RESULTS

Four RCTs and 12 prospective cohort studies met our inclusion criteria, and included a total of 1881 participants with TBM. None of the included RCTs directly compared six months versus longer regimens, so we analysed all data as individual cohorts to obtain relapse rates in each set of cohorts.We included seven cohorts of participants treated for six months, with a total of 458 participants. Three studies were conducted in Thailand, two in South Africa, and one each in Ecuador and Papua New Guinea between the 1980s and 2009. We included 12 cohorts of participants treated for longer than six months (ranging from eight to 16 months), with a total of 1423 participants. Four studies were conducted in India, three in Thailand and one each in China, South Africa, Romania, Turkey and Vietnam, between the late 1970s and 2011.The proportion of participants classified as having stage III disease (severe) was higher in the cohorts treated for six months (33.2% versus 16.9%), but the proportion with known concurrent HIV was higher in the cohorts treated for longer (0/458 versus 122/1423). Although there were variations in the treatment regimens, most cohorts received isoniazid, rifampicin, and pyrazinamide during the intensive phase.Investigators achieved follow-up beyond 18 months after completing treatment in three out of the seven cohorts treated for six months, and five out of the 12 cohorts treated for eight to 16 months. All studies had potential sources of bias in their estimation of the relapse rate, and comparisons between the cohorts could be confounded.Relapse was an uncommon event across both groups of cohorts (3/369 (0.8%) with six months treatment versus 7/915 (0.8%) with longer), with only one death attributed to relapse in each group.Overall, the proportion of participants who died was higher in the cohorts treated for longer than six months (447/1423 (31.4%) versus 58/458 (12.7%)). However, most deaths occurred during the first six months in both treatment cohorts, which suggested that the difference in death rate was not directly related to duration of ATT but was due to confounding. Clinical cure was higher in the group of cohorts treated for six months (408/458 (89.1%) versus longer than six months (984/1336 (73.7%)), consistent with the observations for deaths.Few participants defaulted from treatment with six months treatment (4/370 (1.1%)) versus longer treatment (8/355 (2.3%)), and adherence was not well reported.

AUTHORS' CONCLUSIONS

In all cohorts most deaths occurred in the first six months; and relapse was uncommon in all participants irrespective of the regimen. Further inferences are probably inappropriate given this is observational data and confounding is likely. These data are almost all from participants who are HIV-negative, and thus the inferences will not apply to the efficacy and safety of the six months regimens in HIV-positive people. Well-designed RCTs, or large prospective cohort studies, comparing six months with longer treatment regimens with long follow-up periods established at initiation of ATT are needed to resolve the uncertainty regarding the safety and efficacy of six months regimens for TBM.

Rationality, practice variation and person-centred health policy: a threshold hypothesis

Variation in practice of medicine is one of the major health policy issues of today. Ultimately, it is related to physicians' decision making. Similar patients with similar likelihood of having disease are often managed by different doctors differently: some doctors may elect to observe the patient, others decide to act based on diagnostic testing and yet others may elect to treat without testing. We explain these differences in practice by differences in disease probability thresholds at which physicians decide to act: contextual social and clinical factors and emotions such as regret affect the threshold by influencing the way doctors integrate objective data related to treatment and testing. However, depending on a theoretical construct each of the physician's behaviour can be considered rational. In fact, we showed that the current regulatory policies lead to predictably low thresholds for most decisions in contemporary practice. As a result, we may expect continuing motivation for overuse of treatment and diagnostic tests. We argue that rationality should take into account both formal principles of rationality and human intuitions about good decisions along the lines of Rawls' 'reflective equilibrium/considered judgment'. In turn, this can help define a threshold model that is empirically testable.

A high-resolution computed tomography-based scoring system to differentiate the most infectious active pulmonary tuberculosis from community-acquired pneumonia in elderly and non-elderly patients

OBJECTIVE

The objective of this study was to use high-resolution computed tomography (HRCT) imaging to predict the presence of smear-positive active pulmonary tuberculosis (PTB) in elderly (at least 65 years of age) and non-elderly patients (18-65 years of age).

METHODS

Patients with active pulmonary infections seen from November 2010 through December 2011 received HRCT chest imaging, sputum smears for acid-fast bacilli and sputum cultures for Mycobacterium tuberculosis. Smear-positive PTB was defined as at least one positive sputum smear and a positive culture for M. tuberculosis. Multivariate logistic regression analyses were performed to determine the HRCT predictors of smear-positive active PTB, and a prediction score was developed on the basis of receiver operating characteristic curve analysis.

RESULTS

Of 1,255 patients included, 139 were diagnosed with smear-positive active PTB. According to ROC curve analysis, the sensitivity, specificity, positive predictive value, negative predictive value, false positive rates and false negative rates were 98.6 %, 95.8 %, 78.5 %, 99.8 %, 4.2 % and 1.4 %, respectively, for diagnosing smear-positive active PTB in elderly patients, and 100.0 %, 96.9 %, 76.5 %, 100.0 %, 3.1 % and 0.0 %, respectively, for non-elderly patients.

CONCLUSIONS

HRCT can assist in the early diagnosis of the most infectious active PTB, thereby preventing transmission and minimizing unnecessary immediate respiratory isolation.

KEY POINTS

• HRCT can assist in the early diagnosis of the infectious active PTB • HRCT imaging is useful to predict the presence of smear-positive active PTB • Predictions from the HRCT imaging are valid even before sputum smear or culture results.

How do physicians decide to treat: an empirical evaluation of the threshold model

Background

According to the threshold model, when faced with a decision under diagnostic uncertainty, physicians should administer treatment if the probability of disease is above a specified threshold and withhold treatment otherwise. The objectives of the present study are to a) evaluate if physicians act according to a threshold model, b) examine which of the existing threshold models [expected utility theory model (EUT), regret-based threshold model, or dual-processing theory] explains the physicians’ decision-making best.

Methods

A survey employing realistic clinical treatment vignettes for patients with pulmonary embolism and acute myeloid leukemia was administered to forty-one practicing physicians across different medical specialties. Participants were randomly assigned to the order of presentation of the case vignettes and re-randomized to the order of “high” versus “low” threshold case. The main outcome measure was the proportion of physicians who would or would not prescribe treatment in relation to perceived changes in threshold probability.

Results

Fewer physicians choose to treat as the benefit/harms ratio decreased (i.e. the threshold increased) and more physicians administered treatment as the benefit/harms ratio increased (and the threshold decreased). When compared to the actual treatment recommendations, we found that the regret model was marginally superior to the EUT model [Odds ratio (OR) = 1.49; 95% confidence interval (CI) 1.00 to 2.23; p = 0.056]. The dual-processing model was statistically significantly superior to both EUT model [OR = 1.75, 95% CI 1.67 to 4.08; p < 0.001] and regret model [OR = 2.61, 95% CI 1.11 to 2.77; p = 0.018].

Conclusions

We provide the first empirical evidence that physicians’ decision-making can be explained by the threshold model. Of the threshold models tested, the dual-processing theory of decision-making provides the best explanation for the observed empirical results.

Should malaria treatment be guided by a point of care rapid test? A threshold approach to malaria management in rural Burkina Faso

BACKGROUND

In Burkina Faso, rapid diagnostic tests for malaria have been made recently available. Previously, malaria was managed clinically. This study aims at assessing which is the best management option of a febrile patient in a hyperendemic setting. Three alternatives are: treating presumptively, testing, or refraining from both test and treatment. The test threshold is the tradeoff between refraining and testing, the test-treatment threshold is the tradeoff between testing and treating. Only if the disease probability lies between the two should the test be used.

METHODS AND FINDINGS

Data for this analysis was obtained from previous studies on malaria rapid tests, involving 5220 patients. The thresholds were calculated, based on disease risk, treatment risk and cost, test accuracy and cost. The thresholds were then matched against the disease probability. For a febrile child under 5 in the dry season, the pre-test probability of clinical malaria (3.2%), was just above the test/treatment threshold. In the rainy season, that probability was 63%, largely above the test/treatment threshold. For febrile children >5 years and adults in the dry season, the probability was 1.7%, below the test threshold, while in the rainy season it was higher (25.1%), and situated between the two thresholds (3% and 60.9%), only if costs were not considered. If they were, neither testing nor treating with artemisinin combination treatments (ACT) would be recommended.

CONCLUSIONS

A febrile child under 5 should be treated presumptively. In the dry season, the probability of clinical malaria in adults is so low, that neither testing nor treating with any regimen should be recommended. In the rainy season, if costs are considered, a febrile adult should not be tested, nor treated with ACT, but a possible alternative would be a presumptive treatment with amodiaquine plus sulfadoxine-pyrimethamine. If costs were not considered, testing would be recommended.

Diagnosis of cryptococcal and tuberculous meningitis in a resource-limited African setting

OBJECTIVES

Cryptococcal meningitis (CM) and tuberculous meningitis (TBM) are common in HIV-infected adults in Africa and difficult to diagnose. Inaccurate diagnosis results in adverse outcomes. We describe patterns of meningitis in a Malawian hospital, focusing on features which differentiate CM and TBM with the aim to derive an algorithm using only clinical and basic laboratory data available in this resource-poor setting.

METHODS

Consecutive patients admitted with meningitis were prospectively recruited, clinical features were recorded and cerebrospinal fluid (CSF) was examined.

RESULTS

A total of 573 patients were recruited, and 263 (46%) had CSF consistent with meningitis. One hundred and twelve (43%) had CM and 46 (18%) had TBM. CM was associated with high CSF opening pressure and low CSF leukocyte count. Fever, neck stiffness and reduced conscious level were associated with TBM. A diagnostic index was constructed demonstrating sensitivity 83%and specificity 79% for the differentiation of CM and TBM. An algorithm was derived with 92% sensitivity for the diagnosis of CM, but only 58% specificity.

CONCLUSIONS

Although we demonstrate features associated with CM and TBM, a sufficiently sensitive and specific diagnostic algorithm could not be derived, suggesting that the diagnosis of CM and TBM in resource-limited settings still requires better access to laboratory tools.

Effect of applying a treatment threshold in a population. An example of pulmonary tuberculosis in Rwanda

PURPOSE

Clinicians often think treatment thresholds should be adapted to the setting. We intended to explore the effect in terms of harm because of false negatives and true and false positives of the application of a treatment threshold for pulmonary tuberculosis from a patient's perspective at different prevalence levels in a developing country.

METHODS

In a cohort of 300 patients with chronic cough, we estimated the prevalence of pulmonary tuberculosis, and the sensitivity and specificity of key predictors with latent class analysis (LCA). We computed the post-test probability of individual patients based on these data. With disease- and treatment-related mortality and morbidity, and without cost or regret, we calculated the break-even point of disease probability where treating versus not treating resulted in similar total harm from the patient's perspective. We estimated the total harm of applying this threshold to the cohort, and to hypothetical settings with different disease prevalence.

RESULTS

The threshold was computed at 0.026, suggesting treatment for all patients of the cohort. Hypothetically lowering the prevalence showed that the lowest total harm in the cohort always coincides with this threshold, but that numbers of treated patients drop considerably.

CONCLUSION

For pulmonary tuberculosis a decision threshold solely based on utilities without cost or regret leads to a very low threshold. The lowest total harm is found always at this disease probability, irrespective of the distribution of the patients. Although these findings might suggest an excess prescription at reference level, this is not the case in settings with lower prevalence.

Update on tuberculosis of the central nervous system: pathogenesis, diagnosis, and treatment

Tuberculous meningitis is the most dangerous form of tuberculosis, yet our understanding of disease pathogenesis is based upon studies performed in the 1920s, our diagnostic methods are dependent upon those developed in the 1880 s, and our treatment has advanced little since the introduction of isoniazid in the 1950s. The authors focus this review on three important questions. First, how does Mycobacterium tuberculosis reach the brain? Second, what is the best way of identifying patients who require early empiric antituberculosis therapy? Third, what is the best way of managing tuberculous hydrocephalus?

Evaluation of latent class analysis and decision thresholds to guide the diagnosis of pediatric tuberculosis in a Rwandan reference hospital

SETTING

A pediatric ward of a university hospital in Kigali, Rwanda, a region with a high HIV seroprevalence.

OBJECTIVE

To estimate the diagnostic accuracy of symptoms, signs, and paraclinical investigations for tuberculosis in children, and to propose a clinical rule based on the results.

DESIGN

During a 2-year period all children with cough for more than 2 weeks and/or fever for more than 2 weeks and/or reported weight loss were prospectively included. A set of clinical and paraclinical data were analyzed with latent class analysis. Comparison of post-test probability based on this analysis with a therapeutic threshold for TB was used to develop a guideline.

RESULTS

In the 309 children HIV prevalence was 56%, bacteriology was positive in 9%, and the tuberculin skin test (TST) was >10 mm in 20%. TB prevalence was 32%. Bacteriology and TST had a specificity of 97% and cough had a sensitivity of 91%. Decision analysis suggests treating children presenting one of the inclusion criteria, combined with positive bacteriology or TST >10 mm or contact with a TB patient.

CONCLUSIONS

Latent class analysis confirmed earlier identified predictors for TB and allowed development of an easy to use clinical rule, applicable in reference hospitals of countries with high HIV endemicity.

British Infection Society guidelines for the diagnosis and treatment of tuberculosis of the central nervous system in adults and children

SUMMARY AND KEY RECOMMENDATIONS: The aim of these guidelines is to describe a practical but evidence-based approach to the diagnosis and treatment of central nervous system tuberculosis in children and adults. We have presented guidance on tuberculous meningitis (TBM), intra-cerebral tuberculoma without meningitis, and tuberculosis affecting the spinal cord. Our key recommendations are as follows: 1. TBM is a medical emergency. Treatment delay is strongly associated with death and empirical anti-tuberculosis therapy should be started promptly in all patients in whom the diagnosis of TBM is suspected. Do not wait for microbiological or molecular diagnostic confirmation. 2. The diagnosis of TBM is best made with lumbar puncture and examination of the cerebrospinal fluid (CSF). Suspect TBM if there is a CSF leucocytosis (predominantly lymphocytes), the CSF protein is raised, and the CSF:plasma glucose is <50%. The diagnostic yield of CSF microscopy and culture for Mycobacterium tuberculosis increases with the volume of CSF submitted; repeat the lumbar puncture if the diagnosis remains uncertain. 3. Imaging is essential for the diagnosis of cerebral tuberculoma and tuberculosis involving the spinal cord, although the radiological appearances do not confirm the diagnosis. A tissue diagnosis (by histopathology and mycobacterial culture) should be attempted whenever possible, either by biopsy of the lesion itself, or through diagnostic sampling from extra-neural sites of disease e.g. lung, gastric fluid, lymph nodes, liver, bone marrow. 4. Treatment for all forms of CNS tuberculosis should consist of 4 drugs (isoniazid, rifampicin, pyrazinamide, ethambutol) for 2 months followed by 2 drugs (isoniazid, rifampicin) for at least 10 months. Adjunctive corticosteroids (either dexamethasone or prednisolone) should be given to all patients with TBM, regardless of disease severity. 5. Children with CNS tuberculosis should ideally be managed by a paediatrician with familiarity and expertise in paediatric tuberculosis or otherwise with input from a paediatric infectious diseases unit. The Children's HIV Association of UK and Ireland (CHIVA) provide further guidance on the management of HIV-infected children (www.chiva.org.uk). 6. All patients with suspected or proven tuberculosis should be offered testing for HIV infection. The principles of CNS tuberculosis diagnosis and treatment are the same for HIV infected and uninfected individuals, although HIV infection broadens the differential diagnosis and anti-retroviral treatment complicates management. Tuberculosis in HIV infected patients should be managed either within specialist units by physicians with expertise in both HIV and tuberculosis, or in a combined approach between HIV and tuberculosis experts. The co-administration of anti-retroviral and anti-tuberculosis drugs should follow guidance issued by the British HIV association (www.bhiva.org).