|Values are valid only on day of printing.|
Evaluating patients suspected of having pernicious anemia or immune-mediated deficiency of vitamin B12 with or without megaloblastic anemia
Pernicious anemia (PA) is characterized by atrophic body gastritis (ABG) and is the end state of a progressive disease known as autoimmune chronic atrophic gastritis.(1) In this disease, immune-mediated inflammation leads to destruction of gastric parietal cells with the resultant loss of intrinsic factor production and the inability to absorb dietary vitamin B12. Diagnosis of PA involves demonstrating the presence of a macrocytic anemia in the context of vitamin B12 deficiency, as well as documenting positive autoantibody serology, specifically anti-parietal cell antibody (PCA) and intrinsic factor antibody (IFA).(2) PCAs bind to the alpha- and beta-subunits of the membrane-bound H(+)/K(+)-ATPase. In contrast, IFAs bind directly to intrinsic factor, blocking its ability to bind vitamin B12.(1,2) Both PCAs and IFAs are useful diagnostic markers for PA. In a recently published study, PCAs were 81% sensitive and 90% specific for ABG, while IFAs were 27% sensitive and 100% specific. The study concluded that a combination of PCA and IFA testing was the optimal strategy for the evaluation of patients with suspected PA.(4)
Negative: < or =20.0 Units
Equivocal: 20.1-24.9 Units
Positive: > or =25.0 Units
Reference values apply to all ages.
A positive result indicates the presence of IgG antibodies to H(+)/K(+) ATPase and suggests the possibility of pernicious anemia (PA) or a related autoimmune disease.
A negative result indicates no detectable IgG antibodies to H(+)/K(+) ATPase; it does not rule out PA.
An equivocal result is indeterminate.
The presence of immune complexes or other immunoglobulin aggregates in the patient specimen may cause an increased non-specific binding and produce false-positive results in this assay.
A negative result does not rule out the presence of parietal cell antibodies; the concentration of antibody may be below the detection limit of the assay.
A positive result only indicates the presence of antibody to H(+)/K(+) ATPase and does not necessarily indicate the presence of autoimmune disease or other diseases.
The assay performance has not been established for pediatric patients.
Results of this assay should be used in conjunction with clinical findings and other serological tests.
The assay performance characteristics have not been established for matrices other than serum.
1. Toh BH, Van Driel IR, Gleeson PA: Pernicious anemia. N Eng J Med 1997;337(20):1441-1448
2. Lahner E, Annibale B: Pernicious anemia: new insights from a gastroenterological point of view. World J Gastroenterol 2009;15(41):5121-5128
3. Lahner E, Normal GL, Severi C, et al: Reassessment of intrinsic factor and parietal cell autoantibodies in atrophic gastritis with respect to cobalamin deficiency. Am J Gastroenterol 2009;104(8):2071-2079
4. Product Insert: QUANTA Lite GPA, INOVA Diagnostics, Inc., San Diego, CA