Inhalation of myc. tuberculosis proliferation in alveoli Spread via the lymphatic system The infection is contained. Hypersensitivity to tuberculoprotein positive skin test possible reactivation in the futur: =Post primary TB Proliferation of the infection hilar nodes enlargment bronchus, alveolar, pleural involvment =Primary TB Hematogenous dissemination: pulmonary miliary and extra-pulmonary TB
The diagnosis of pulmonary TB: The usual ways in the context of a developing country: * Microsopic examination of sputums for research of acid fast bacillus. (AFB) Reminder: Acid-fastness is a physical property of some bacteria referring to their resistance to decolorization by acids during staining procedures Less frequent : * Chest radiography * Skin test with tuberculine * Biopsy specimen and anatomo-pathology (pleural biopsy, endoscopic biopsy…)
5 The diagnosis of pulmonary TB (2) More sophisticated ways in developed countries culture + Antibiogram: useful for multi-resistant TB Molecular genetic methods: Polymerase chain reaction usefull for diagnosis of TB and resistance to rifampicin and isoniazid
Main bacteriological techniques (1) Microsopic examination of sputum for research of acid fast bacillus by Ziehl coloration or auramine TPM+ this examination detects contagious patients, who have a pulmonary tuberculosis (TPM+). It is a screening for patients who cough and spit and who have a sufficient quantity of bacilli in sputum to be detected: > 5000/ ml These patients are the most contaminating patients
But TPM- are numerous « pauci-bacillar » cases : < 5000 bacilli per ml in sputum:-Nodular tuberculosis (non-excavated) « pauci-bacillar » cases : < 5000 bacilli per ml in sputum:-Nodular tuberculosis (non-excavated) -miliary -miliary - tubercular adenopathy - tubercular adenopathy - extra-pulmonary cases (EPT) - extra-pulmonary cases (EPT) Too weak patients who cannot produce sufficient sputum for bacterial analysis or are not cooperating (salivary sputum…) Too weak patients who cannot produce sufficient sputum for bacterial analysis or are not cooperating (salivary sputum…) Treatment has begun before screeningTreatment has begun before screening Technical error in the research of AFB.Technical error in the research of AFB.
But radiological aspects of TB are numerous and not always specific In cases of TPM- the physician must decid of TB treatment on clinical and radiological datas Differential diagnosis are numerous, especially in case of Coinfection with HIV Nodules : TPM- Infiltrates: TPM-/+ Cavities: TPM+ Pneumoniae: generally TPM+ Miliary: TPM- Pleural effusion: TPM- Adenopathies: TPM- Séquella (inactive or not :TPM- / M+)
10 The efficiency of the microscopic examination increases with the repetition of the samples ( Al Zahrani and coll. Int j. tuber. Lung dis. Sept 2005) Sample number Positive sample with Ziehl % positive culture 16693 27697 38499 485100
11 Main bacteriological techniques (2) culture The culture by the classical method (Lowenstein culture medium): – A bit difficult, rather high cost, delayed results (1 to 2 months after the initial sample), –Especially useful for tuberculosis with few bacilli which cannot be diagnosed by direct microscopic examination: TPM- and EPT
12 Main bacteriological techniques (3) Other forms of culture The gelose culture medium (Middlebrook medium) 3 to 4 weeks (instead of 4 to 6 with the traditional method). The liquid culture medium: – radioactive medium (Bactec system) – non-radioactive medium (MGIT) Can detect bacilli in 8 to 14 days.
13 Molecular genetic methods: PCR ( Polymerase Chain Reaction) genomic amplification technique: specific DNA probes can identify different mycobacteria. Advantage: Results in 24 to 48 h, very good specificity (97% to 98%). Result in les than 2 hours with system X pert MTB/RIF Test Disadvantage: low sensitivity in comparison to the culture (+/-80%), high cost, but progress with more recent systems (Accuprobe ®, Genprobe®)
4 Sample automatically filtered and washed 5 Ultrasonic lysis of filter-captured organisms to release DNA7 6 DNA molecules mixed with dry PCR reagents7 7 Seminested real-time Amplification and detection in integrated reaction tube 1 Sputum liquefaction and inactivation with 2:1 sample reagent 2 Transfer of 2 ml material into test cartridge 3 Cartridge inserted into MTB-RIF test platform (end of hands-on work) 8 Printable test result Résults in less than 2 hours X pert MTB/RIF Test
15 Sensitivity tests: antibiograms Indirect antibiogram: after obtaining colonies with culture (results 2 to 3 months after initial sample). Direct antibiogram, only possible if the initial sample contains very many bacili. (results in 4 - 6 weeks). Difficult technique, high cost, delayed results. Routinely, this test is not necessary for treatment of the majority of patients. It is very useful if there is any suspicion of resistance
17 Q1. What is the role of the chest x-ray in the national TB program (1)? Rich and developped countries: respiratory symptoms chest radiography(x-ray) The chest x-ray is not recommended Developing countries: The chest x-ray is not recommended in first intention (recommandations of OMS and UICTMR) TB treatment without chest x-ray If TPM+: TB treatment without chest x-ray If TPM- x 3 and persistance of symptoms after non-specific antibiotic, the national program recommands chest x-ray
The radiography cannot make, as microscopy, a definite diagnosis of TB, because radiological aspects of TB are varied and often non-specific.The radiography cannot make, as microscopy, a definite diagnosis of TB, because radiological aspects of TB are varied and often non-specific. But some images are very indicative of TB. Some others images must invoke differential diagnosis. But some images are very indicative of TB. Some others images must invoke differential diagnosis. The chest radiography is essential for TPM(-) TB. It is necessary for the physicians to be able to make a correct analysisThe chest radiography is essential for TPM(-) TB. It is necessary for the physicians to be able to make a correct analysis >>> TPM- diagnosis is often made in excess, with a useless treatment and failure to spot or diagnose another pathology. >>> TPM- diagnosis is often made in excess, with a useless treatment and failure to spot or diagnose another pathology. Q1. What is the role of the chest x- ray in the national TB program (2)
19 Disagreement between clinician and radiologist about the analysis of the chest radiography Evaluation Percentage of disagreement Detection of a cavity 28% Pulmonary abnormality 34% Adenopathy60% Pulmonary calcification 42% Deterioration between 2 chest x-rays 30% Deciding whether an abnormality is TB or not TB 45%
3 distinct situations: The chest x-ray strongly suggests TB.The chest x-ray strongly suggests TB. The chest x-ray does not remotely suggest TBThe chest x-ray does not remotely suggest TB The chest x-ray could suggest TB, but differential diagnoses are certainly possible.The chest x-ray could suggest TB, but differential diagnoses are certainly possible. Whatever the situation, it is always important to confront patient history, clinical signs, bacteriology and radiology Whatever the situation, it is always important to confront patient history, clinical signs, bacteriology and radiology
21 Q2. What is the role of the tuberculin skin test ? A tuberculin skin test is sometimes useful for the diagnosis of TB (contact with contagious patient) The interpretation of a test result is often very difficult: -False positive : BCG vaccination, technical error in injection or in the induration measurement, other mycobacterial infection -False negative : technical error in injection or in the induration measurement, viral infection, immunodepression, anergic time (+/- 40 days)…
22 Q3. Who should be considered a case of TB? 1 smear (+) examination for TB should be recorded as smear positive (TPM+). All other cases should be recorded as smear negative (TPM-) or as extra- pulmonary cases (EPTB).
INTRODUCTION The diagnosis of EPTB is difficult and sometimes requires sophisticated means: Surgical biopsies and anapath. examination Bacterial samples obtained by puncture with culture if possible BUT…in developing countries, these techniques are not always available
INTRODUCTION(2) Aids epidemy: gradual increase of percentage of EPTB If a bacteriological or anapath sample doesnt exist, the diagnosis is made with the association of clinical, biological, radiological arguments and sometimes with the analysis of the evolution under TB treatment
Main forms of EPTB Serous membrane TB Pericarditis pleuritis Peritonitis Adenopathies Miliary Genital and urinary Bones Neuro meningeal Hepatic and intestinal multivisceral
Diagnosis procedure (1) Type of EPTB Presumption criteriaDifferential diagnosis Certitude criteria Pleural TB. Clinical and radiological signs. Pleural effusion: - serofibrinous -Protein > 30g or ratio or fluid.prot / serum prot.> 0.5 -lymphocytes 80 to 100% - Neoplasic effusion -Non-TB infectious disease -Others… Positive culture of liquid. Positive culture and anapath. of biopsy specimen.
Diagnosis procedure (2) Type of EPTB Presumption criteriaDifferential diagnosis Certitude criteria Node TB Clinical signs indicative localisation (cervical, mediastinal...) Cancer, lymphoma, Non-TB infectious disease … Puncture and biopsy: AFB+ at microscopic examination. Positive culture and anapath
Diagnosis procedure (3) Type of EPTB Presumption criteriaDifferential diagnosis Certitude criteria TB meningitis Clinical context Cerero-spinal fluid: -clear fluid -CSF cell count: lymphocytosis 30 to 500/mm3 -CSF protein: >100mg /dl -CSF glucose: < 0.5 glycemy -Fungal (cryptococcus) - Bacterial (beginning of infection or pre-treated) -Neoplasic -viral meningo- encephalitis (herpes simplex) AFB+ in CSF (infrequent) India ink – Culture + (but late result)
Diagnosis procedure (4) Type of EPTB Presumption criteriaDifferential diagnosis Certitude criteria TB peritonitis Abdominal pain, fever, weight loss, sub- occlusive syndrome Ascitis without portal hypertension or cirrhosis Ultrasound: mesenteric adenopathies Fluid: -lemon yellow color -leucocyte count: 150 to 4000/mm3 (lymphocitic) -protein>30 g/l -serum/ascite gradiant albumine <1.1 -peritoneal carcinomato sis -Pancreatic ascite -non-TB poly microbial infection (beginning) Laparoscopy and biopsy specimen for anapath Examination and culture: (Multiple whitish nodules on visceral and parietal peritoneum)
Diagnosis procedure (5) Type of EPTB Presumption criteriaDifferential diagnosis Certitude criteria Spinal TB (=TB of the vertebra) -Local pain +++indolent on the beginning>>delay in diagnosis>>>neurologic Sequela -Sometimes local abcess (cold abcess) -++Radiological findings (but not specific): osteolytic lesion with or without disc involvment, on 1 or many levels ( chest x-ray normal in > 50% of cases) Staphyloccocus brucellosis, Histoplasmosis Infection. Bone metastasis. Biopsy: culture and anapath exam. of the infected bone: But rarely possible in DC, except if soft tissue abcess
Diagnosis procedure (5) Type of EPTB Presumption criteriaDifferential diagnosis Certitude criteria Genito- urinary Tuberculosis Dysury, steril pyuri, hematury Combination of upper and lower tract involvment female: pelvic chronic pain, sterility, salpingitis ectopic pregnancy Male: epydidymitis and orchi-epidydimitis Non-TB genital and urinary infection AFB+ or culture+ in urine, menses Endometrial biopsy Laparoscopic biopsy