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Use of plasma methylmalonic acid in diagnosing vitamin B-12 deficiency in general practice
Anne-Mette Hvas1, Jørgen Lous, Jørgen Ellegaard
1Department of Haematology, Aarhus University Hospital, Denmark. am.hvas@dadlnet.dk
Objectives:
To examine the reasons why general practitioners (GPs) request plasma methylmalonic acid (MMA) tests and how they respond to a result above the reference interval.
Design:
Retrospective study of medical records.
Setting:
Primary health care, Aarhus County, Denmark.
Subjects:
181 patients with increased concentrations of plasma MMA ( > 0.28 micromol/l) attending 10 GPs.
Main Outcome Measures:
Reasons for requesting the analysis and reactions to a plasma MMA level above the reference interval.
Results:
A reason for requesting plasma MMA was stated in 129 (71%) of the 181 medical records, screening being the most frequent. A reaction to an increased concentration of plasma MMA was recorded in 128 (71%) patients, and vitamin B-12 treatment was initiated in 102 (80%) of them. Among the 105 patients with marginally elevated plasma MMA level (0.29-0.44 micromol/l), vitamin B-12 treatment was initiated in 38 (36%).
Conclusion:
Plasma MMA was frequently used as a screening test. Treatment with vitamin B-12 was initiated when MMA level was increased, and often when plasma MMA level was slightly above the reference interval. This strategy is likely to promote over-treatment with vitamin B-12.