Isoniazid (+ N-Acetyl-Isoniazid)

Sample type: Whole Blood Collected in Sodium Oxalate/Potassium Fluoride Grey Top Tube

Test name: Isoniazid (+ N-Acetyl-Isoniazid)

Condition / Indication: Requesters have found these assays to be of value in patients with difficult infections or in patients that are failing to respond to treatment.

Advance warning: Not usually required, advanced warning only needed for Weekends and Public Holidays.

Special precautions & notes: Blood should be collected in Grey-topped Sodium Fluoride/Potassium Oxalate (Fx) tube and sent as whole blood - unspun and unseparated

Sample required: Approx. 1-2 mL of blood taken in Grey-topped Sodium Fluoride/Potassium Oxalate (Fx) tube. Sample must be sent as whole blood (unspun and unseparated) to lab within 5 days of being taken.

Timing of samples: We recommend a post dose sample, taken 2 hours after the end of administration (and/or 6 hours if monitoring absorption). 

Test information required: • Patient name, sex and age
• Laboratory number
• Dosage, frequency and timing of samples
• Clinical Summary
• Address for report
• Phone (fax if preferred) number for report or email address for an electronic copy
• Contact name
• Appropriate hazard warnings

Results: Results will be telephoned/faxed or emailed on the day of receipt for samples received between 9am and 3pm Monday to Friday. A written confirmation report will be sent by post.

Reference range: Isoniazid Post dose: 3.0 – 5.0 mg/L ; N-Acetyl Isoniazid Post dose: N/A (indicator of rate of isoniazid metabolism to the inactive form).

Container: Grey top Sodium Fluoride/Potassium Oxalate

Alternative container: None.

Ideal volume (mL): 1-2 ml

Referred outside NBT for analysis? No

Discipline: Antimicrobial Reference Laboratory

Turnaround time: <3 days (from day of receipt)

Re-assay interval:
3-5 days post dose adjustment