Sample type: Serum

Test name: Flucytosine

Condition / Indication: Requesters have found these assays to be of value in all patients with renal impairment or also receiving amphotericn B.

Advance warning: Not normally required during our core working hours (Mon – Fri 09:00 – 17:15). Please contact laboratory to discuss the possibility of this assay being performed on Saturdays, Sundays and Bank Holidays.

Sample required: Approx. 1-2mL of separated serum (the minimum acceptable is 100µL). It is best to use a plain clotted blood tube for collection but if a gel tube is used it is important for the requesting laboratory to separate off the serum from this primary gel tube into a secondary tube as soon as possible. This is because the gel may bind the analyte which may result in an artificially lower result being obtained, interpreted and reported.
Samples may be sent by post. Transport time must be <4 weeks. Samples should be kept at 4°c if there is a delay in sending. Please contact laboratory if in doubt as sample integrity may be affected. Samples must be sealed and packed to conform to current regulations. Leaking samples may not be processed.

Timing of samples: We recommend pre dose sample and a post dose sample, taken 1 hour after the end of iv administration.

Test information required: • Patient name, sex and age
• Laboratory number
• Dosage, frequency and timing of samples
• Clinical Summary
• Other medications (essential)
• 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 9 am and 3 pm Monday to Friday. A written confirmation report will be sent by post.

Reference range: Pre dose 20-50 mg/L
Post dose 50-100mg/L
Pre dose concentrations <20 mg/L have been associated with treatment failure and emergence of resistance.
Post dose concentrations >100 mg/L have been associated with toxicity.

Container: Serum (from a non-gel tube)

Referred outside NBT for analysis? No

Discipline: Antimicrobial Reference Laboratory

Turnaround time: < 2 days

Re-assay interval: 4-8 Days – Assuming initial results are within expected range.