2ICS & PTB

1. What is the correct way to identify the second intercostal space? (Hint: sternal angle)

2. What are the criteria to diagnosis PTB (pulmonary tuberculosis)? (Hint: 2/3 criteria)

3. What is TB intensive and maintenance/continuation phase? (hint: type of medication and duration)

1. Second intercostal space:

• The angle of Louis / sternal angle is a useful place to start counting ribs, which helps localize a respiratory finding horizontally. If you find the sternal notch, walk your fingers down the manubrium a few centimeters until you feel a distinct bony ridge. This is the sternal angle. The 2nd rib is continuous with the sternal angle, slide your finger down to localize the 2nd intercostal space.
• The angle of Louis also marks the site of bifurcation of the trachea into the right and left main bronchi and corresponds with the upper border of the atria of the heart.

2. Diagnosis criteria of PTB (2/3):

1. Clinical picture of PTB: cough >2-3/52, fever, LOW, +/- hemoptysis
2. CXR signs of PTB: Upper lobes consolidation / cavitation
3. Sputum AFB (+): 3 x early morning sputum is collected on first day, subsequent 1 x early morning sputum for another 3/7.

However, before diagnosis can be put as PTB, we can consider whether to give anti-TB drugs after collecting the sputum. Signs that suggest PTB (but not enough to diagnose it):

• Clinical picture of PTB
• CXR signs of PTB
• FBC changes: ↑ Monocyte, ↑ Platete, ↑ ESR

If the above signs are fulfilled, it is highly suggestive for PTB, and anti-TB drugs can be given after sputum is collected. Remember to check for serum Na+ to exclude SIADH. 

3. TB treatment:

• Intensive phase of refer to the initial phase of TB treatment, 2/12 duration, on 4 anti-TB drugs. Aims: Eliminate clinical picture of TB, eliminate MTB in sputum, and prevent development of drug resistance.
  
  e.g. 2HRZE or 2HRZS
  
  
• Maintenance/continuation phase refer to the second phase of TB treatment, 4-7/12 duration, on 2 anti-TB drugs. Aims: Suppress MTB in host, and prevent relapse of TB.
  
  e.g. 4HR or 4(HR)3

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Answers:

1. The sternal angle is between the manubrium and sternum. Once you identify the location by palpation, the left second rib is just beside it. Your finger moves along the second rib and move down below it. There the second intercostal space is localized. The importance of localization of second intercostal space is to do pleurocentesis, chest tube insertion and etc.

2. The criteria of PTB diagnosis:
a. Clinical symptoms
b. CXR findings
c. Sputum AFB(acid fast bacilli)

• Clinical symptoms: in your clerking, you must ask duration of cough, hemoptysis, evening rising temperature, night sweat, LOA/LOW (loss of appetite and loss of weight), h/o (history of) contact with PTB patients, h/o PTB in the past, risk factor (e.g DM, IVDU/Intravenous drug user, RVD+ve/retroviral disease +ve, so on). The symptoms must be more than 2 weeks duration.
  
• CXR findings: cavitation/haziness over upper zone/apical region of lung field.
  
• Sputum AFB: collection must be done x OD x 3/7

REMEMBER: to diagnose PTB, we need 2 out of 3 criteria.
TB is divided into PTB and EPTB (extrapulmonary PTB). PTB can be smear positive and smear negative.
Even sputum AFB is negative, with 2 other criteria, evidence is enough to label a patient with smear negative PTB. Smear positive PTB is PTB with sputum AFB +ve.
Note: sputum AFB is not sputum MTB.

3. TB intensive phase usually requires 2 months or 56 doses. The initial phase can be extended up to maximum, 84 doses, depending on the patient's condition. During this phase, the standard TB medication would be EHRZ / Ethambuthol + Isoniazid + Rifampicin + Pyrazinamide.
Then the latter phase would be continuation/maintenance phase. During this phase, the standard anti-TB medication would be H (Isoniazid) and R (Rifampicin). It is given at least 6 months.

You must know the common side effect of PTB medication.

• E - 15-25mg/kg/day; max 1200mg
  common SE- optic neuritis
  contraindicated for the patient with advanced age > 70 years old and age < 15 years old, poor vision, renal impairment.
  
• H - 5mg/kg/day; max 300mg
  common SE- liver impairment, skin rash.
  
• R - 10mg/kg/day; max 600mg
  common SE- liver impairment, acute renal failure, thrombocytopenia, drug-induced jaundice
  
• Z - 25mg/kg/day; max 1500mg
  common SE- liver impairment, hyperuricemia

S(Streptomycin)- used when it is indicated. Usually it is given for TAI (treatment after interruption), relapsed TB, reactivation of TB. Common SE- renal impairment, ototoxicity. It is contraindicated in age > 60 and in children, pregnancy.

Another way of TB prescription according to weight. It is used by chest physician in Kedah.

• S - Streptomycin
  0.75mg OD if BW > 30kg;
  0.5mg OD if BW < 30kg
  
• H - Isoniazid
  300mg OD
  
• R - Rifampicin
  600mg OD if BW > 50kg;
  450mg OD if BW 30-50kg and
  300mg OD if BW < 30kg
  
• Z - Pyrazinamide
  1500mg OD if BW >40-50kg;
  1250mg OD if BW 30-40kg and
  1000mg OD if BW < 30kg
  
• E - Ethambutol
  by practise 1400mg OD up to maximum 2600mg OD and we calculate 25mg/kg/day for E

TB medication is mainly prescribed by chest MO; however we need to know the usual dosage.

TB is the second main infectious disease after Dengue fever.

Additional Question:

What are signs of TB of CNS on neuroimaging? (There should be 5)

1. Tuberculoma: non-enhancing and enhancing.
2. Infarct: caused by vasculitis after being insulted by TB granulation tissue
3. Hydrocephalus: communicating and non-communicating
4. Meningeal enhancement, especially basal enhancement

Not sure about the last sign, but might be the following:

1. Cerebral abscess: rare complication
2. Cerebritis with enhancement at cerebral parenchyma
3. Granulation tissue in basal cistern, superficial sulcal spaces, Sylvian fissure
    → Isodense or mildly hyperdense exudate obliterates the basal cistern.
4. Cerebral oedema