What is the most used diagnostic method of tuberculous before kidney transplantation, to exclude latent tuberculosis infection, Tuberculin skin test or IGRA?
Tuberculin test is of low specificity and has many false positive and false negative reactions
It depends on where you are.
If you are in a very poor country, TST is an affordable option, despite the low specificity and approximately 20% of false negative responses.
Certainly IGRA is more specific, as you can use several M. tuberculosis specific antigens to determine the immune response to mycobacterial species, so if you have access to IGRA it is certainly a better option.
Moreover, due to the huge number of different species of mycobacteria with several cross-reacting molecules, the possibility of a positive TST directed to an environmental mycobacteria is real.
In countries endemic for tuberculosis both can present with doubtful and difficult to interpret results.
Another point to consider is that if the patient is uremic the chances of a negative TST despite previous contact (and even possible disease) to M. tuberculosis are really high. If the doubt persists, probably the best option is to treat the patient preemptively.
It would depend on the patient at the time, a TST is usually done as a diagnostic for LTBI, but if their immune system is compromised then the TST may not mount a positive response (if they were indeed positive). In that case, a history of the patient would also help determine if an IGRA would be better option. Especially if they have had a BCG vaccine.
IGRA is more sensitive in patients with impaired cellular immunity , and have low cross-reactivity with BCG and other mycobacteria.
Nienhaus,A, Schablon A, Costa JT, and Diel R. Systematic review of cost and cost-effectiveness of different TB-screening strategies.BMC Health Serv Res. 2011; 11: 247.
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