Mbs reviews vitamin b12 testing report february 2014 table of contents section Page
REVIEW OF GUIDELINES RELEVANT TO VITAMIN B12 TESTING
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- 4.1.2 International Guidelines
4 REVIEW OF GUIDELINES RELEVANT TO VITAMIN B12 TESTINGThis Chapter presents the results of the literature search for clinical practice guidelines relevant to vitamin B12 testing. 4.1 Clinical practice guidelines4.1.1. Australian GuidelinesNo Australian guidelines were identified that made recommendations on vitamin B12 testing. 4.1.2 International GuidelinesInternational guidelines related to the use of vitamin B12 vary widely in their recommendations. While some recommend vitamin B12 testing as a screening tool in commonly encountered illnesses such as dementia, others suggest restricting testing to patients who have already undergone pre-test investigations (such as full blood examinations and blood film examination). A rapid review from the Division of Evidence Development and Standards at Health Quality Ontario (see Chapter 5.1 for further details) identified three guidelines on the diagnosis of vitamin B12 deficiency.(71) The three guidelines(72-74) were assessed using the AGREE appraisal tool(75). The recommendations from each of the guidelines are listed in Table 4.1. Two of the guidelines were systematic reviews with recommendations.(72, 73) The guideline by the British Columbia Medical Association and Ministry of Health was not explicitly based on a systematic review of the literature. In the methods that are reported on the website that published the guideline, the authors state that a full systematic review may not be conducted for all of their guidelines. As a result, it is unclear whether this guideline was based on the results of a systematic review. The three guidelines scored poorly on linking the evidence to the recommendations.(71) A further nine guidelines, eight of which focused on specific clinical conditions or patient populations, were identified in the literature search for clinical practice guidelines. Relevant recommendations from these guidelines are summarised in Table 4.1. Table 4.1: Guidelines relating to vitamin B12 testing
Guidelines from the British Columbia Guidelines and Protocols Advisory Committee (2012)(74) recommend performing a full blood count, blood film and serum cobalamin in all patients suspected of cobalamin deficiency. The guidelines recommend interpreting serum cobalamin levels in light of clinical symptoms, because the test has the following limitations:(71)
The best practice review by Smellie et al. (2005)(73) on the diagnosis and monitoring of vitamin B12 (and folate) deficiency was based on a standardised literature search of national and international guidance notes, consensus statements, health policy documents, and evidence based medicine reviews, supplemented by relevant primary research documents. However, the authors of the best practice review stated that the recommendations were mostly ‘consensus rather than evidence based’. Therefore, the guidance/recommendations were derived from a small number of reviews, supplemented by extrapolations from knowledge of the physiology of vitamin B12 and folate. The best practice review recommended that vitamin B12 (and folate) testing should be performed in patients with macrocytic anaemia, macrocytosis, and specific neuropsychiatric abnormalities (including paraesthesia, ataxia, peripheral neuropathy, and memory loss).(73) The systematic review by Andres et al (2004)(72) used a flow chart or care pathway to describe recommendations. A notable difference in the guideline by Andres et al (2004) was that the authors recommended screening all patients in institutions or psychiatric hospitals for vitamin B12 deficiency. Andres et al (2004) reported that the prevalence of vitamin B12 deficiency was much higher (30% to 40%) in patients who were sick or institutionalised. As mentioned above for the British Columbia Medical Association guideline, there was a very weak relationship between the recommendations and the evidence presented in all guidelines. The British Committee for Standards in Haematology (BCSH) published a review entitled "Guidelines on the investigation and diagnosis of cobalamin and folate deficiencies" in 1994(76). Although now very dated, this publication highlighted that vitamin B12 deficiency was synonymous with macrocytic anaemia, but that many patients with pernicious anaemia may present without either anaemia or macrocytosis.(76) However, emphasis on haematological indices and blood film examination is strong and the authors did not provide comment on the relative merits of various laboratory and test procedures nor on appropriate testing algorithms. There are several guidelines that focus on specific clinical conditions, which indicate that serum vitamin B12 levels should be assessed. The clinical conditions include (but not limited to) cognitive impairment(79, 80), dementia(81), Crohn’s disease(84) and chronic fatigue syndrome(82). The guideline published by the British Columbia Medical Association and Ministry of Health on cognitive impairment in the elderly stated that data from systematic reviews of RCTs (only one of which was cited, Malouf et al. (2003)(85) did not provide evidence of improvement in cognition or dementia with vitamin B12 treatment. In addition, many guidelines recommended the evaluation of vitamin B12 deficiency in the workup for clinical indications without specifying a methodology. An exception is in a practice parameter for peripheral neuropathy by the American Academy of Neurology (AAN) that has specified a methodology (evidence level C): screening for “serum B12 level with metabolites (methylmalonic acid with or without homocysteine)” in the evaluation for vitamin B12 deficiency in all patients with distal symmetric polyneuropathy.(83) Yüklə 404,62 Kb. Dostları ilə paylaş:
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