C5 Isobars

Description: 
The C5 isobar test is a second line screening test which is indicated when an increased C5 carnitine result is obtained by Newborn Screening Programme Centre. Four different isobars (isovalerylcarnitine, pivaloylcarnitine, valerylcarnitine and 2-methylbutyrylcarnitine) can contribute to C5 increase. The aim of the test is to identify which compound is present in the sample to aid interpretation of the screening result.
Reference range: 

Qualitative analysis only - results are reported as an interpretive comment.

Department: 
Biochemical Sciences Department
Location: 
Blackfriars Hub
Sample type and Volume required: 
Capillary blood spotted onto a Newborn Screening blood spot card (Guthrie card). Minimum one spot of 7 mm diameter.
Call in advance: 
Yes
Turnaround time: 
Same day from SE Thames NBS lab, five working days for samples from external NBS laboratories.
Special sample instructions: 

Allow to dry at room temperature prior to packaging. 

Criteria for acceptance / rejections of sample
Storage and transport: 
Send via first class post. Samples should be received within the laboratory within 14 days of collection.
Contacts:
Inherited Metabolic Diseases Unit at Blackfriars Hub
07592 502653
Reference Chemistry, 1st Floor Blackfriars Hub
Friars Bridge Court
Blackfriars Road
London
SE1 8NZ
For clinical advice or interpretation of results, please contact the laboratory in the first instance.
Laboratory: 
Reference Chemistry at the Blackfriar's Hub

Print as a PDF

Last updated: 08/10/2025