Hello every body.
Tuberculosis is a very common disease and encountered very often specially in a disease poor country. Pulmonary TB is perhaps the commonest form of TB that you can see in the outpatient departments and medical clinics. It is not limited to the underprivileged, just the circumstances of its occurence are different in those living in well ventilated homes, who are well fed and not commonly in contact with sick people. When are you likely to encounter TB more commonly and in which communities?
You are going to encounter it in times of community or social stress. For example among refugees in camps and among them after they have reached safe haven specially if they are considered illegal by the countries where they have sought a life of safety i.e. either poverty or enforced poverty, in prisons specially where prisoners of war are kept. In a previously healthy person why has TB become active and why is the patient now showing signs of the disease?
- Economic stress: someone has lost a job and cannot eat well because of lack of money. They have had to move out of a good neighbourhood because they cannot pay their rent and are now living in a crowded, poorly ventilated house with poor sanitation. They have been thrown out of the family home specially women. They have retired and lost their economic status and their son who was supporting them has stopped sending money. They have been sent to prison. One of these scenarios may apply. If you are aware you can ask the right questions.
- Stress associated with substance abuse and HIV: have become addicted to an expensive substance like cocaine or methamphetamine or alcohol. Have lost their job because of it and have become a sex worker to pay for their drug habit. Have acquired HIV as a result.
- Stress of some other new disease or its treatment: newly acquired diabetes. out of control diabetes, use of steroids as in asthma or for a renal transplant, use of chemotherapy.
- Exposure to a high dose of Mycobacterium i.e. some very ill relative has come to stay with them or they have visited someone in a hospital.
When are you likely to encounter TB in the well to do? What questions will you need to ask them if you suspect that TB is causing the problem?
- Have you recently visited a place where you are likely to have encountered patients with TB; like a hospital visit for charity reasons, visit to a prison or a visit to a hospice or charity that caters to drug addicts,
- Have you recently employed a poor person in your home who is likely to have tuberculosis or have some one at home who has TB?
- Are any of your children ill? Remember that children pick up TB from the environment much more quickly than adults and then will pass it on to adults who care for them.
- Is any one at your place of work unwell?
- Do you have diabetes and is it out of control?
- Are you taking any drugs for another illness like bronchial asthma, rheumatoid arthritis, chronic diarrhoea or an organ transplant?
- Are you taking any drugs from a hakim or practitioner of alternate medicine which have made your asthma or arthritis suddenly disappear? Since osteoarthritis is so common that patients are likely to seek “quick relief fixes” in the form of very high dose steroids in the form of capsules or added to majuns and other medicines dispensed by unlicensed by the government.
- Please show me the list of drugs that you are taking. Look for deltacortil, dexamethasone, methotrexate, cyclosporin (Sandimune) et.
Candidates ask a lot of questions in the history most of which are from a list that they have memorised and are not relevant to the case, If you are not dealing with a waterborne disease then do not ask for a history of the type of water they drink. The question will sound silly to the examiner and you will appear clinically immature.
In a previously healthy patient you are likely to be asked: why did this person acquire TB at this point in time? The answer the examiner is seeking is ” It is either activation of a dormant infection or an encounter with a patient with a heavy load of infection.” You will then be asked “When does a dormant infection activate and is there evidence in the history that the patient encountered a heavy dose of bacteria?” Be prepared with the answer. Anticipate these questions and seek the answer in the history.
A typical example is a 60-year-old man with low-grade fever for four months along with weight loss, poor appetite, night sweats who has a small palpable spleen and liver and looks malnourished. Disseminated TB is a possible diagnosis. He was a house painter who had lost his job 8 months ago because of arthritis of the wrists, He was unmarried and became dependent on his nephew whom he had supported in the past. This young man was already supporting a wife and six children on an income of 16000 rupees and lived in a 2 bedroom house. You can imagine the crowding and inadequacy of the diet.
Other questions to anticipate and prepare for:
- How will you confirm your diagnosis of disseminated TB? An X-ray chest may show faint reticuloendothelial miliary shadows (miliary from the size of a millet seed). these take 3-6 weeks to develop so may not show on chest X-rays taken very early. this represents nodular interstitial spread. with significant alveolar involvement. “Acinar nodules” are described as larger (5 to 10 mm) and more heterogeneous than classic miliary TB, but overlap occurs, making the appearance of many of these conditions indistinguishable. These conditions are alveolar hemorrhages, early pulmonary edema, inhalational diseases which may come into the D/D of miliary shadows. Other findings may be pleural effusion, hilar lymphadenopathy and old lesions of TB which may be inactive like an old cavity or fibrosis. If you see these please mention that these are either inactive or the source of the current infection.
- A raised ESR, CRP and anemia are supportive but not diagnostic and only indicate on-going chronic inflammation, sputum tests are not an option because the patient is not producing sputum and mycobacteria will not be present in the saliva.
Microbial diagnostic tests are difficult to obtain and may be negative. Please read my blog on Microbiological diagnosis og TB
Other questions you are likely to be asked:
- What are the hematological feature of disseminated TB? Leucopenia, thrombocytopenia, lymphocytosis are the common ones along with iron deficiency anemia. DIC may occur and cause a drop in Hb and a bleeding tendency. Leucocytosis is rare though a leukemoid reaction will make it necessary to exclude acute leukemia. A bone marrow aspiration biopsy may need to be done also in case of pancytopenia, it will show focal granulomata.
- What is the histological structure of a tuberculous granuloma? Why does caseation necrosis occur? Why does fibrosis and cavity formation occur? Will all cases of miliary TB end up with a fibrosed lung? Look up the answers; this is a blog not an encyclopedia. Be prepared.
- What is DOTS therapy and when is it employed? Why is anti-TB therapy always with multidrugs and not just one drug? Should you treat contacts and if so for how long and with which drugs. Be prepared.
- In MDR TB will you start an entirely new regime or a regime based on isoniazid and rifampicin along with second line drugs and why? All the mycobacteria are not multidrug resistant and those that are sensitive respond much better to INH and rifampicin than they do to second line drugs which are on their own less effective, so INH and rifampicin are included in all the MDR regimes.
- Why does a pleural effusion develop in miliary TB? Seeding of the pleura causing an acute inflammatory reaction and an outpouring of exudative fluid. If you centrifuge the pleural fluid there is a 40% chance that mycobacteria will be seen on a slide and the fluid can be cultured for mycobacteria. You can do an NAA test on the fluid (PCR). Ditto for peritoneal fluid and pericardial fluid.
- What drugs will you give a pregnant woman with TB?
- How will you treat liver TB ans TB in the presence of liver dysfunction?
- How will you modify ATT in renal failure? Which ATT will interfere with immunosuppression in a renal transplant. remember 10-12 % of transplant patients are likely to develop TB because of immunosuppression. Will you give BCG vaccine to an immunosuppressed patient? Be prepared.
I have based this blog on the questions the candidates were not able to answer in the FCPS 2 exam or in the short case in IMM. Please prepare yourself with all the answers.