Add On Tests

We are aware that on occasion it is necessary to request additional tests for a sample already in the laboratory.

Most tests are stable, and may be added to a properly stored sample (see below for sample retention times.) Some are more labile and may not be added on outside certain time intervals.

We will accommodate additional requests where possible, provided that:

The appropriate specimen type with sufficient sample remaining is available.
The test does not require special specimen handling which may be incompatible with prior processing of the specimen.

There are 2 main methods by which additional tests may be requested:

Via phone to the laboratory – 01392 402962
- For urgent additions only
Via email – rduh.microconsultants@nhs.net
- For non-urgent additions

Information required for all requests is as follows:

Name, Date of Birth and NHS number of patient
Tests to be added
Any additional relevant clinical details
Name and contact number of requester

Sample retention times:

Specimens are retained in the laboratory for a defined length of time in line with guidance from the Royal College of Pathologists (RCPath.)

Specimens sent for bacteriological culture may deteriorate over time. If the delay to add-on test is greater than 48 hours after the specimen has been received in the laboratory it is preferable to take another sample if possible.

Sample Type	Retention Period
Swabs for MC&S	7 days
Tissues/Fluids/CSF for MC&S	6 weeks
Urines for Culture	72 hours
Respiratory Samples for MC&S	7 days
Faeces for Culture	7 days (For C.diff testing – samples must be less than 72hrs old – to avoid false negatives due to sample degradation.)
Routine Serology Bloods	6 months
Antenatal Serology Bloods	2 years
Donor Serology Bloods	10 years
Swabs & Urines for Chlamydia/Gonorrhoea PCR	72 hrs
Respiratory PCR Swabs	72 hrs
Swabs for HSV/VZV PCR	7 days
Bloods for BK/CMV/EBV PCR	2 weeks
Bloods for HBC/HCV/HIV PCR	Plasma/Serum Aliquots kept for 4 weeks
Faeces for Molecular Tests (e.g. Norovirus)	48hrs