Suggestions for a clinical approach to asymptomatic, hematologically normal patients with suspected subclinical cobalamin deficiency
| Notes . | Comments . |
|---|---|
| Diagnostic | |
| A low serum cobalamin (< 200 or 250 ng/L) is not automatically diagnostic for cobalamin deficiency in asymptomatic, hematologically normal patients. | 22% to 30% of such cobalamin levels are falsely low. |
| A cobalamin level of 200 to 350 ng/L does not reflect cobalamin deficiency at all in 65% to 78% of such cases. | |
| At least two unrelated biochemical abnormalities should be sought to diagnose deficiency (eg, cobalamin and MMA) because an isolated biochemical abnormality (eg, MMA alone) may also be spurious, unless confirmed by its normalization with cobalamin therapy. | Results of all tests are unreliable in the face of renal insufficiency. Cobalamin and holotranscobalamin II values may be too closely linked to provide independent confirmation of each other. |
| Greatly elevated metabolite levels (eg, MMA >1000 nmol/L) require serious attention. | Mildly abnormal metabolite levels are often evanescent. |
| Always test for intrinsic factor antibody (despite its poor sensitivity) in a patient with suspected cobalamin deficiency. | Although PA is rare in subclinical deficiency, its diagnosis implies clinical disease and transforms management. |
| Therapeutic | |
| A monitored cobalamin trial is warranted for the patient with sufficiently suspicious clinical findings. | A cobalamin trial is not needed for a marginal, isolated metabolic abnormality unless compelling reasons exist. |
| The cobalamin trial should be parenteral. If given orally, 1000-μg doses should be given daily for 4 weeks. | Injection or high oral doses are preferred because absorption often cannot be determined. |
| In a trial, clinical and laboratory reassessment should be done 4 to 8 weeks after injection. | Retest suspicious clinical findings as well as metabolic abnormalities. |
| Duration of therapy depends on the underlying disorder. | |
| Follow-up every 1 to 3 years is warranted in all patients with unknown causation or unclear course. | Follow-up should include clinical reevaluation and cobalamin and MMA assay. |
| Notes . | Comments . |
|---|---|
| Diagnostic | |
| A low serum cobalamin (< 200 or 250 ng/L) is not automatically diagnostic for cobalamin deficiency in asymptomatic, hematologically normal patients. | 22% to 30% of such cobalamin levels are falsely low. |
| A cobalamin level of 200 to 350 ng/L does not reflect cobalamin deficiency at all in 65% to 78% of such cases. | |
| At least two unrelated biochemical abnormalities should be sought to diagnose deficiency (eg, cobalamin and MMA) because an isolated biochemical abnormality (eg, MMA alone) may also be spurious, unless confirmed by its normalization with cobalamin therapy. | Results of all tests are unreliable in the face of renal insufficiency. Cobalamin and holotranscobalamin II values may be too closely linked to provide independent confirmation of each other. |
| Greatly elevated metabolite levels (eg, MMA >1000 nmol/L) require serious attention. | Mildly abnormal metabolite levels are often evanescent. |
| Always test for intrinsic factor antibody (despite its poor sensitivity) in a patient with suspected cobalamin deficiency. | Although PA is rare in subclinical deficiency, its diagnosis implies clinical disease and transforms management. |
| Therapeutic | |
| A monitored cobalamin trial is warranted for the patient with sufficiently suspicious clinical findings. | A cobalamin trial is not needed for a marginal, isolated metabolic abnormality unless compelling reasons exist. |
| The cobalamin trial should be parenteral. If given orally, 1000-μg doses should be given daily for 4 weeks. | Injection or high oral doses are preferred because absorption often cannot be determined. |
| In a trial, clinical and laboratory reassessment should be done 4 to 8 weeks after injection. | Retest suspicious clinical findings as well as metabolic abnormalities. |
| Duration of therapy depends on the underlying disorder. | |
| Follow-up every 1 to 3 years is warranted in all patients with unknown causation or unclear course. | Follow-up should include clinical reevaluation and cobalamin and MMA assay. |