Understanding laboratory tests: Appropriate laboratory tests for Chronic Variable Immune Deficiency
On the 17 June 2013 the Daily Mail published an article with the headline ‘Do you catch every bug going? A top-up of fresh blood could be the answer’ reporting on a case of Chronic Variable Immune Deficiency (CVID). Lab Tests Online-UK provides a response to some factual errors contained within the article.
- The test that should be requested to diagnose CVID is Immunoglobulin (also called an antibody), but this test is not used for the diagnosis of anaemia or infection.
- Immunoglobulins are measured in grams per Litre (g/L), not immunoglobulin per litre.
- The reference range quoted is not applicable to all patients. The concentration of immunoglobulin within the blood changes according to the age of the patient. NHS laboratories report Immunoglobulin results (often IgG, IgA and IgM) with age-specific reference ranges, therefore the normal range reported in the article is not relevant to all age groups.
- “Full blood count immunoglobulin” is not a recognised test. Full blood count and immunoglobulin are two different blood investigations.
- The FISH test, Fluorescence in situ hybridization, is a technique used to evaluate genes and DNA, and unrelated to this disease investigation.
Dr Joanna Sheldon, Consultant Clinical Scientist in Immunology and Director of the Protein Reference Unit, St Georges Healthcare NHS Trust commented that:
“CVID is a rare condition that affects approximately 6000 of the UK population but patients generally respond well to treatment once the diagnosis has been made. The most important test to do if you are thinking about antibody deficiency is to measure the concentration of the antibodies (also called immunoglobulins) in the blood.
It is important that patients have accurate information about laboratory tests and they understand that serum immunoglobulin measurements are not the same as a full blood count, are not the tests appropriate to check for anaemia and the test is not called a FISH test.”
Dr Danielle Freedman, Chair of the Lab Tests Online-UK Board
“Lab Tests Online believe it is crucial that patients are given the correct information about laboratory testing, in order to engage in their own healthcare with their GP or other healthcare professionals.”
Dr Aarn Huissoon, Consultant Immunologist, Birmingham Heartlands Hospital
“I regret the multiple errors in the article, which may cause confusion both regarding laboratory testing and about the condition itself and its treatment. The article was based on interviews with myself and the patient, but was unfortunately published without our further input or review.
Naturally, I agree with all the clarifications above. I would add that in this context “FISH” is an acronym intended to help doctors remember what tests to request when they initially consider immunodeficiency: Full blood count, Immunoglobulin, Serum complement and HIV test. This is expanded on in a recent article that can be accessed here: http://rcpjournal.org/content/11/4/380.full.pdf+html
The Daily Mail article headline and online illustrations also give the misleading impression that blood transfusions are used to treat CVID, although the text makes it clear that the treatment is immunoglobulin, which is prepared from blood donations.
While these errors are regrettable, I hope the article will still serve its main purpose which is to raise the profile and awareness of immunodeficiency as a commonly missed and delayed diagnosis.”