Non-radioactive schilling test
The present invention relates to a new method named the COBASORB test, which can be used for testing the cause of cobalamin malabsorption in humans. The COBASORB test contains three separate tests (first, second and third test) that can be performed separately, sequentially or in random order and number. The first test uses non-radioactive cobalamin for ingestion, the second test uses non-radioactive cobalamin and recombinant intrinsic factor for ingestion and the third test uses recombinant haptocorrin saturated with cobalamin for ingestion. All three tests involve analysis of changes in the concentration of cobalamin saturated transcobalamin (holo-TC) and cobalamin saturated haptocorrin (holo-HC) in the blood. Also disclosed are kits suitable for use in these methods.
1 - 41 . (canceled)
42 . A method for determining absorption of vitamin B12 in an individual comprising the steps of:
i) providing two blood samples from said individual, wherein the first sample was taken before ingestion by said individual of non-radioactive cobalamin or an analogue thereof, together with binding protein or without a binding protein, and
the second sample was taken after said ingestion,
ii) determining in said samples one or more selected from the group consisting of: the concentration of holo-TC, the concentration of holo-HC, the saturation of TC and the saturation of HC, and
iii) determining, on the basis of comparison of said concentration and/or saturation in said two samples, whether said cobalamin or analogue thereof has been absorbed in the blood stream.
43 . The method according to claim 42 , wherein said non-radioactive cobalamin or analogue thereof was ingested without a binding protein.
44 . The method according to claim 42 , wherein said non-radioactive cobalamin or analogue thereof was ingested together with intrinsic factor or an analogue, fragment or variant thereof.
45 . The method according to claim 44 , wherein said intrinsic factor or analogue, fragment or variant thereof is of recombinant origin.
46 . The method according to claim 44 , wherein said intrinsic factor or analogue, fragment or variant thereof is derived from a recombinant plant.
47 . The method according to claim 42 , wherein said non-radioactive cobalamin or analogue thereof was ingested together with
haptocorrin or an analogue, fragment or variant thereof or
another binding protein that can serve as surrogate for cobalamin binding proteins in food.
48 . The method according to claim 47 , wherein said haptocorrin or analogue, fragment or variant thereof or said other binding protein is of recombinant origin.
49 . The method according to claim 47 , wherein said haptocorrin or analogue, fragment or variant thereof or said other binding protein is derived from a recombinant plant.
50 . The method according to claim 43 , further comprising the step of ingesting: intrinsic factor or an analogue, fragment or variant thereof.
51 . The method according to claim 42 , wherein two or more doses of cobalamin (together with a binding protein or without a binding protein) are ingested.
52 . The method according to claim 51 , wherein the cobalamin was ingested three times at six hours intervals.
53 . The method according to claim 42 , wherein the total ingested dose of cobalamin was between 0.5 and 500 nanomole.
54 . The method according to claim 52 , wherein each of the three ingested doses was between 5 and 15 nanomole.
55 . The method according to claim 42 , wherein the determination of one or more selected from the group consisting of:
the concentration of holo-TC, the concentration of holo-HC, the saturation of TC, and the saturation of HC,
is performed less than 48 hours after the last ingestion of cobalamin.
56 . The method according to claim 55 , wherein the determination of one or more selected from the group consisting of:
the concentration of holo-TC, the concentration of holo-HC, the saturation of TC, and the saturation of HC,
is performed 8-16 hours after the last ingestion of cobalamin.
57 . The method according to claim 50 , wherein the initial determination of one or more selected from the group consisting of:
the concentration of holo-TC, the concentration of holo-HC, the saturation of TC, and the saturation of HC,
for the subsequent method is performed more than 48 hours after the last ingestion of cobalamin in the previous method.
58 . The method according to claim 57 , wherein the initial determination of one or more selected from the group consisting of:
the concentration of holo-TC, the concentration of holo-HC, the saturation of TC, and the saturation of HC,
for the subsequent method is performed 5-10 days after the last ingestion of cobalamin in the previous method.
59 . The method according to claim 50 , wherein the cobalamin, together with or without the binding protein, was ingested in the same amount, in the same number of doses, with the same number of hours between doses in each method.
60 . The method according to claim 50 , wherein the determination of one or more selected from the group consisting of:
the concentration of holo-TC, the concentration of holo-HC, the saturation of TC, and the saturation of HC,
in the blood is performed at the same time after the ingestion of cobalamin, together with or without binding protein, in each method.
61 . The method according to claim 42 , wherein the concentration of holo-TC and/or holo-HC is measured by immunosorbent assay.
62 . The method according to claim 61 , wherein the immunosorbent assay is an ELISA or RIA.
63 . The method according to claim 61 , wherein the holo-TC and/or holo-HC concentration is determined by subtracting the concentration of apo-TC and/or apo-HC from the total concentration of TC and/or HC.
64 . The method according to claim 61 , wherein the apo-TC and/or apo-HC are removed by passing the sample over cobalamin complex to a solid phase support.
65 . The method according to claim 63 , wherein the concentration of apo-TC and/or apo-HC is determined by using monoclonal antibodies specific for apo-TC or apo-HC.
66 . The method according to claim 61 , wherein the concentration of holo-TC and/or holo-HC is determined by using monoclonal antibodies specific for holo-TC or holo-HC.
67 . The method according to claim 42 wherein the holo-TC or holo HC concentration is determined by measurement of the vitamin B12 attached to holo-TC or holo-HC.
68 . The method according to claim 67 , wherein the determination comprises the following steps:
separation of both apo- and holo-form of TC or HC from the sample by binding to antibodies against TC or HC;
release of the cobalamin from the holo-TC or holo-HC fraction and removal or destruction of the TC or HC;
determining the amount of cobalamin released by a competitive binding assay.
69 . The method according to claim 42 , wherein the final determination step comprises determining whether any one or more selected from the group consisting of:
the holo-TC concentration, the holo-HC concentration, the TC saturation and the HC saturation,
in the second sample is higher than in the first sample.
70 . A method for the evaluation of a possible vitamin B 12-related deficiency in an individual comprising the steps of the method of claim 42 , and further comprising the step of evaluating, on the basis of comparison of said concentration and/or saturation in said samples, whether said individual suffers from a vitamin B12-related deficiency and/or what the cause of said deficiency is.
71 . A method for determining the cause of a vitamin B12-related deficiency in an individual comprising the steps of the method of claim 42 , and further comprising the step of evaluating, on the basis of comparison of said concentration and/or saturation in said samples, what the cause of said deficiency is.
72 . A method for evaluating whether a vitamin B12-related deficiency is due to an intrinsic factor deficiency, such as lack of intrinsic factor secretion, or to a malabsorption of intrinsic-factor-bound cobalamin in the intestine, said method comprising the carrying out the method of claim 44 , and further comprising the step of evaluating, on the basis of comparison of said concentration and/or saturation in said samples, whether a vitamin B12-related deficiency is due to a lack of secretion of intrinsic factor or to a malabsorption of intrinsic-factor-bound cobalamin in the intestine.
73 . A method for evaluating whether a vitamin B12-related deficiency is due to a deficient transfer of cobalamin from food to intrinsic factor, said method comprising carrying out the method of claim 47 , and further comprising the step of evaluating, on the basis of comparison of said concentration and/or saturation in said samples, whether the vitamin B12-related deficiency is due to a deficient transfer of cobalamin from food to intrinsic factor.
74 . A method for diagnosing a vitamin B12 deficiency in an individual comprising the steps of:
i) obtaining a blood sample from an individual,
ii) having said individual ingest a dose of non-radioactive cobalamin or an analogue thereof, together with a binding protein or without a binding protein,
iii) obtaining, after a time period sufficient to allow uptake, if any, of the cobalamin or analogue thereof in the blood stream, a second blood sample from said individual,
iv) determining in said samples one or more selected from the group consisting of: the concentration of holo-TC, the concentration of holo-HC, the saturation of TC and the saturation of HC, and
v) determining, on the basis of comparison of said concentration and/or saturation in said two samples, whether said cobalamin or analogue thereof has been absorbed in the blood stream.
75 . A kit-of-parts suitable for use in the diagnosis of a vitamin B12-related deficiency, comprising
i) materials suitable for determining the holoTC and/or holoHC concentration in a blood sample, and
ii) instructions to the user comprising a description of the possible use of the kit in carrying out the method defined in claim 42 .
76 . The kit-of-parts according to claim 75 , wherein the materials for determining the holoTC and/or holoHC concentrations comprise antibodies to transcobalamin and/or antibodies to haptocorrin.
77 . The kit-of-parts according to claim 75 , further comprising non-radioactive cobalamin.
78 . The kit-of-parts according to claim 75 , further comprising intrinsic factor and/or haptocorrin.
79 . The kit-of-parts according to claim 75 , further comprising cobalarnin bound to a solid support and/or buffers, plastic material and substrates necessary determining the concentration of holo-TC and/or holo-HC.
80 . The kit-of-parts according to claim 75 , further comprising labelled cobalamin.