Miliary TB is a form of severe and active TB disease signifying dissemination of the TB bacilli to the lung parenchyma and other organs. TB Quantiferon-Gold and TST (Tuberculin skin test or the Mantoux test) are not diagnostic for any form of active TB disease including miliary TB but are used for detection of Latent TB infection (LTBI). LTBI occurs when the bacilli establish infection within lymphocytes and tissue macrophages and remain in a dormant state or latency, with no replication. Diagnosis of Latent TB infection can be made using Quantiferon gold or TST but diagnosis of active TB disease including miliary TB requires identification of the acid-fast bacilli on microscopy or molecular tests for the genetic material (DNA) using the GeneXpert or other molecular tests.

In miliary TB, the immune response may be suppressed due to systemic disease or immunosuppression (e.g., HIV), leading to false-negative QFT-G results. Therefore, QFT-G is not reliable for diagnosing miliary TB. Diagnosis of miliary TB should rely on clinical presentation, radiological findings (e.g., diffuse micronodular pattern on chest imaging), histopathology, and direct detection of M. tuberculosis via acid-fast bacilli staining, culture, or molecular methods such as GeneXpert or PCR. In summary, QFT-G is useful for latent TB screening but not for diagnosing disseminated forms like miliary TB.

You have to be cautious because miliary tuberculosis is severe presentation of TB which means that that immune system has failed almost completely so do not wait to find positive results of gamma interferon … I mean the can be negative.

There is a difference between TB Infection and TB disease the later being a progression from the later as a result of inability to contain the mycobacterium within the lympho and tissu macrophages. The organisms begin to replicate and multiply and begin to cause disease and damage to tissue including miliary or disseminated tuberculosis. At this stage the organisms are available in the affected tissue and other tissue fluids like sputum, cerebrospinal flui, urine and stool, specimens from these sites can be analyzed by acid fast microscopic examination, molecular techniques like the geneXpert or phenotypic process by cultires either by liquid or solid medium as in MGIT and LJ media to demonstrate active , viable and multiplying mycobacterium species which can be subjected to further molecular assays to determine types and drug susceptibility or resistance.

Higher level of gamma interferon is found during the infection phase after that if the infection goes on with diseases the levels of it begin to decrease up to levels below of diagnostic value.

Tuberculin skin test is not a diagnostic for tuberculosis, rather hypersensitive reaction to tuberculin antigen. In immunosuppression, both the described so called diagnostics may give false negative result. This researcher had done several studies on tuberculosis diagnostics which are simple., sensitive, cost-effective, reproducible. His published articles may be gone through and valuable critical observation may be put forward.