Modern approaches to the investigation of vitamin B12 deficiency

Ward, Patrick C. J.

doi:10.1016/s0272-2712(01)00003-8

Cited by 35 publications

(39 citation statements)

References 44 publications

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“…Serum MMA will be elevated in patients with underlying renal dysfunction, decreasing its specificity and sensitivity in identifying patients with cobalamin deficiency. 23 Similarly, hereditary homocysteinemia is a condition in which the serum homocysteine levels are elevated. Measurements of MMA levels are recommended when initial vitamin B12 and/or homocysteine levels are abnormal.…”

Section: Rbc Folatementioning

confidence: 99%

“…41 HoloTC II can also be used in cases of renal failure or myeloproliferative diseases in which vitamin B12 concentrations may be falsely elevated. 23,42 HoloTC II is a metabolically active protein that transports cobalamin to cell membrane receptors. Its serum concentration can be used to measure the amount of vitamin B12 attached to the binding protein transcobalamin II.…”

Section: Holotranscobalamin II (Holotc Ii)mentioning

confidence: 99%

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Megaloblastic Anemia and Other Causes of Macrocytosis

Aslinia¹,

Mazza²,

Yale³

2006

Clinical Medicine & Research

284

214

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The term macrocytosis refers to a blood condition in which red blood cells (RBC) are larger than normal. Macrocytosis is reported in terms of mean corpuscular volume (MCV). Normal MCV values range from 80 to 100 femtoliters (fl) and vary by age and reference laboratory. 1 MCV is calculated according to the following formula:Macrocytosis can be identified by reviewing peripheral blood smears and/or by automated RBC indices. The peripheral blood smear is more sensitive than RBC indices for identifying early macrocytic changes because the MCV represents the mean of the distribution curve and is insensitive to the presence of small numbers of macrocytes. 2 However, compared to the peripheral blood smear, MCV may underestimate macrocytosis in over 30% of cases. 3 Although determination of the MCV by automated blood cell counter is rarely inaccurate, hyperglycemia, marked leukocytosis and cold agglutinins may result in false elevations of the MCV. [4][5][6] Moreover, partial occlusion of the instrument aperture and/or leaving the blood sample at room temperature for several hours may also result in false elevations of the MCV value. Clinical SignificanceMacrocytosis is a relatively common finding in the era of automated blood cell counters, with prevalence estimates ranging from 1.7% to 3.6%. 3,7,8 Its significance tends to be underestimated by physicians, since about 60% of patients present without associated anemia, 8 unless there are other accompanying abnormalities noted.No complications arise from macrocytosis itself as an isolated finding. However, its identification can provide important information regarding the presence of an underlying disease state. Thus, in the appropriate clinical setting, MCV values above the upper limit of normal or those that differ significantly from the patient's baseline values may require further clinical and laboratory assessment to determine the underlying cause of the macrocytosis. 9

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Section: Rbc Folatementioning

confidence: 99%

Section: Holotranscobalamin II (Holotc Ii)mentioning

confidence: 99%

Megaloblastic Anemia and Other Causes of Macrocytosis

Aslinia¹,

Mazza²,

Yale³

2006

Clinical Medicine & Research

284

214

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“…Performance of these tests has been increasingly difficult because of the limited availability of radioactively labeled vitamin B 12 and decreasing acceptance of a radioactively labeled vitamin in a diagnostic test (2 ). Moreover, the IF of human origin used in these tests has been removed from the market in most countries.…”

Section: Discussionmentioning

confidence: 99%

“…All available tests, including the classic Schilling test, rely on measurement of radioactively labeled vitamin B 12 after an oral dose of the vitamin (1 ). The use of a radioactively labeled compound has made the tests increasingly unacceptable (2 ). An alternative approach is therefore needed for estimation of the absorption of vitamin B 12 .…”

mentioning

confidence: 99%

Nonradioactive Vitamin B12 Absorption Test Evaluated in Controls and in Patients with Inherited Malabsorption of Vitamin B12

et al. 2005

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Background: Current tests for evaluation of vitamin B 12 absorption are problematic because they involve the use of radioactively labeled vitamin B 12 . We describe a vitamin B 12 absorption test that circumvents this problem. Methods: We measured cobalamin or transcobalamin saturated with cobalamin (holo-TC) 24 h after three 9-g doses of vitamin B 12 given orally at 6-h intervals. We studied 17 patients with inherited malabsorption of vitamin B 12 attributable to Imerslund-Grasbeck syndrome (n ‫؍‬ 13) or intrinsic factor deficiency (n ‫؍‬ 4), their obligate heterozygous biological parents (n ‫؍‬ 19), and healthy controls (n ‫؍‬ 44).

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“…The standard test for vitamin B 12 absorption is the Schilling test. The Schilling test is problematic mainly because it uses labeled vitamin B 12 and because it requires normal renal function, a complete 24-h urine collection, and large parenteral doses of vitamin B 12 that can occasionally obscure the diagnosis (11)(12)(13). There thus is a need to find alternative tests for estimating vitamin B 12 absorption to both diagnose the cause of vitamin B 12 deficiency and estimate the absorptive capacity of the small intestine.…”

Section: Discussionmentioning

confidence: 99%