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:
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||48hrs|