FOOD SENSITIVITY: THE CYTOTOXIC TEST
This involves taking a blood sample, extracting the white blood cells (immune cells), and then exposing them to food extracts. The theory behind the test is that if a patient is sensitive to a particular food it will affect the white blood cells, causing changes that are visible under a microscope. In severe reactions, the white blood cells are said to swell up and break open.
Scientific appraisals of the cytotoxic test show that food extracts do sometimes affect the white blood cells in this way, and a recent study under carefully controlled conditions produced 65-70 per cent accuracy. Tests sometimes show a reaction to foods which the patient can eat without getting any symptoms (a false positive) or they may fail to pick up a known food sensitivity (a false negative). Quite apart from these fundamental problems with the test itself, many of the commercial laboratories offering the test do not seem to be all that good at it. Even when they are sent two samples of the same blood, they fail to give a consistent result.
There may well be some value in the cytotoxic test, but not as currently practised. Scientific attempts to improve it are going on at present – in particular, the assessment of the reaction by the blood cells needs to be automated, so that it is more objective. At present, the reaction is assessed by someone looking down a microscope, and the results are highly subjective, varying greatly from one person to another. A more accurate version of the test may be available in a few years time, but at present it is not worth the money.
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