Table 4.

Summary of proposed ENDA protocol for performing and reading drug intradermal test.

1. IDT must be performed, following negative prick tests, using pharmaceutical grade human drugs in injectable form. IDT is contraindicated in severe cutaneous adverse drug reactions

2. Syringe size and needle gauge: • Tuberculin syringe of preferably 0.5 ml or if not available, 1-ml volume • Needle gauge of 25, 27, or 30 G • Same fixed or new needle can be used for test IDT

3. Injection technique: - Adopt sterile techniques. - Fill syringe with test solution; change the needle if not fixed. Tap the barrel of the syringe to make the air bubble rise to the needle end of the syringe. Expel air bubble and excess volume pushing the plunger to the 0.02-ml mark on the barrel (Figure 1). A syringe with a flat end plunger is better than one with a tapered end to help measure the volume of the test solution drawn into the syringe. - With the bevel of the needle facing upward, pierce skin tangentially in the upper dermis (at about 10° angle to the skin surface). - Then slowly inject the measured volume intradermally.

4. Control: - After intradermal injection of 0.02 ml of saline or test solution at recommended concentration, an injection wheal measuring 4.5- to 5.5-mm diameter should form. - If no clear wheal forms, repeat injection.

5. Record all injected solutions, batch number, and map of injection sites. Draw around and/or measure the diameter of the immediate injection wheal (Wi). If you surround the wheal with ink, always measure the inner diameter.

6. Read the IDT after 20 min. Measure wheal (W20) and surrounding erythema (E20).

7. If the wheal is not round, measure the length (L), then the width (w) taken perpendicularly, in the middle of the axis length Wi = (L+w)/2.

8. In patient records and publications, IDT results must be recorded as follows: Wi, W20, and E20.

9. At 20 min, the IDT is considered positive only if there is a wheal, W20 ≥ Wi + 3 mm and surrounding erythema, E20.

10. For delayed reactions read at 24, 48 h, or later (please specify the time interval). IDTs are considered positive when there is an erythematous induration or swelling at the injection site.