Diagnosis

1. QuantiFERON®-TB Gold Plus (QFT®-Plus) ELISA package insert. Germany: QIAGEN; 2019 (http://www.quantiferon.com/wp-content/uploads/2017/04/English_QFTPlus_ELISA_R04_022016.pdf)
2. Campbell J, Pease C, Daley P, Pai M, Menzies D. Diagnosis of tuberculosis infection. In: Menzies D (ed), Canadian tuberculosis standards – 8th edition.

The T-SPOT.TB has multiple steps (4). These steps are detailed below and shown in Fig. A2.3.1 (for sample preparation and testing procedures) and in Fig. A2.3.2 (for interpretation).

Step 1. Blood-sampling procedures

The procedures for collecting blood samples are similar to those of the QFT-Plus, except that direct blood draw into the incubation tubes is not recommended. Instead, blood samples are drawn into lithium heparin tubes and then transferred into the N, T and P tubes. One millilitre of whole blood sample is transferred into each of the test tubes. These tubes are then placed directly in a 37 °C ±1 °C incubator within 2 hours, and incubated for 20–24 hours. These steps are detailed below (3) and shown in Fig. A2.2.1 (up to incubation) and Fig. A2.2.2 (after incubation).

Step 1. TB screening

The first step is to screen for TB, as outlined in Step 1 for tuberculin skin test (TST) or Mycobacterium tuberculosis antigen-based skin test (TBST) in Annex 1.

Step 2. Explain the administration of QFT-Plus

This annex provides step-by-step procedures for administering and reading three interferongamma release assays (IGRAs) for tuberculosis (TB): QFT-Plus, WANTAI TB-IGRA and T-SPOT.TB.

Step 1. Seeing the patient

Patients should be seen as quickly as possible after they arrive for the reading of their TST or TBST. Reading of the test takes less than 3 minutes on average (7). If a person must wait a long time simply for the result to be read, this may discourage other contacts in the same household from coming forward for testing or reading, and may discourage the same person from having a re-test, if needed.

Step 2. Re-check symptoms

Step 1. TB Screening