Suitable Specimen Types
- Plain Spot Urine
- EDTA Whole Blood
- Faeces
Specimen Transport
Send to referral laboratory overnight at room temperature, protected from light.Sample Processing in Laboratory
Usual. All specimens must be protected from light.Sample Preparation
All specimens should be protected from light. Indicate on request form if specimens not protected from light.Turnaround Time
2-3 weeksSample Stability
Stable at 4 ºC for up to one week but should be referred to Cardiff the next working day.Porphyrins/Porphyria analysis (Urine/Faecal/Blood specimens)
General Information
The porphyrias are uncommon disorders of haem biosynthesis and their effective management requires prompt and accurate diagnosis.
Laboratory investigations depend on the clinical presentation and/or family history, therefore as much information as possible should be included with the request, e.g. medications, alcohol, any family history.
Ideally all specimens collected should be sent to the referral laboratory. Analysis will only be performed on all specimens if front line tests and/or clinical picture indicate that analysis is required. For further information regarding sample choice strategies please use the links on Sample Choice Strategies - Cardiff and Vale University Health Board (nhs.wales) where testing/sample choice strategies are defined by the clinical picture
NB: Screening for active cutaneous porphyria can be achieved by blood porphyrin screen alone. However, urine and faecal porphyrin analysis may be required to distinguish between certain cutaneous porphyrias and to support subsequent monitoring of treatment. It may therefore be more cost effective to send urine and EDTA blood for frontline testing.
For further information regarding the test repertoire, specimen types and clinical utility of different investigations refer to:
Porphyria Test Repertoire 2020/2021 - Cardiff and Vale University Health Board (nhs.wales)
Patient Preparation
Specimens should be collected whilst patient symptomatic if acute porphyria is suspected. See attached document/cardiff-porphyria.org for advice on which specimen types should be collected depending on presentaion and/or history.
Information required for Reference Lab: Full patient name, REG Number and DOB. Relevant clinical information, particularly whether neurological or dermatological symptoms are present. Whether patient was symptomatic at the time specimens were collected.
If part of a family study the name of the proband.
Notes
Summary of porphyrin analyses that may be performed (refer to sample choice strategy links above for advice regarding which specimen types to send):
Urine analysis (early morning urine preferred)
- Total porphyrins and PBG analysed on all samples (UPORPH/UPOR). If positive total porphyrins, HPLC fractionation will be performed (discretion of referral laboratory; UPOR2)
- ALA if pre-pubertal and/or clinical picture indicates (at discretion of referral laboratory; UALA)
Blood analysis
- Plasma scan front line test (BPOR1)
- If not protected from light and ?cutaneous porphyria/?acute photosensitivity, RBC screen will be performed (BPOR2). If positive, total RBC protoporphyrin analysis performed (BPOR3)
Faecal analysis (generally only performed if urine/blood results and/or clinical picture indicates)
- Total faecal porphyrins and HPLC fractionation (FPOR)
Handling Samples in the labortatory prior to sending to referral lab
Samples that are not wrapped to protect them from light exposure but are received in the lab less than 6 hours after collection can be assayed. Please add a comment to the request form stating that exposure to light has occurred. The referral lab will include this on the report and advise that the results should be interpreted taking this into account. This will allow the requesting clinician to decide whether they wish to repeat the tests.
However in patients with active porphyria, porphyrin concentrations are greatly increased and would remain detectable despite light exposure over this time period.
Sarnples exposed to light for greater than 6 hours should not be assayed. The samples should be discarded and repeat samples requested straight away, particularly if the patient is still on-site.
Please contact the referral lab if you would like to discuss individual cases as factors such as patient symptoms, type of porphyria suspected, family history of porphyria and sample availability may inform further advice.
Reference Range
Reference ranges provided by Cardiff Porphyria Service.