I notice that a number of you are searching for information about the above tests. Well, none of them are particularly good - yet. The Active B12 Test (Holotranscobalamin or HoloTC) shows some promise as a front line test to establish the B12 Status of patients but it still needs further development while the MMA and HCy tests need further investigation. See the interview with Dr Dominic Harrison who has been supervising the HoloTC test for several years at St Thomas' Hospital in London in my latest book. I also discuss the possible use of Hcy and MMA as a front line test.
Incidentally, the book also examines and analyses the new Guidelines on Cobalamin and Folate issued by the British Committee for Standards in Haematology in 2014 (following lobbying by the PA Society at the Dept of Health) and the guidelines state quite plainly that if the patient has the symptoms of B12 Deficiency but there is discordance between the symptoms and the test result then treatment should be started straight away to prevent any nerve damage. The guidelines acknowledge that the current test to ascertain the B12 status of patients is next to useless. Similarly the new guidelines state that the test to determine whether any deficiency is due to Intrinsic Factor Antibodies is also flawed and patients can test positive or negative and still have Pernicious Anaemia.
My book also gives some details of new tests that have and are being developed to correct this problem of current tests being unreliable which leads to misdiagnosis and wrong diagnoses - leading to unnecessary suffering.
It's all in the book!