Chemistry: analytical and immunological testing – Including sample preparation – Stabilizing or preserving
Reexamination Certificate
1998-05-28
2001-07-24
Jones, Deborah (Department: 1775)
Chemistry: analytical and immunological testing
Including sample preparation
Stabilizing or preserving
C436S164000, C436S808000
Reexamination Certificate
active
06265223
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the general area of remote site blood sample collection for medical diagnostic tests. More specifically, the invention relates to medical diagnostic tests using filter paper to collect the blood sample.
DISCUSSION OF THE RELEVANT ART
Historically, blood samples have been drawn from a patient in a hospital or physician's office using an evacuated test-tube to collect blood from a venipuncture by a physician, nurse, or other medical professional. Alternatively, a method for sampling of blood at a site remote from the hospital, physician's office, or laboratory has developed over the years where a small amount of blood may be obtained from a fingerstick and the blood can be absorbed onto filter paper to collect the sample. This is known in the art as a “dry” technique, as opposed to a “wet” remote site sampling technique that involves collection of a blood sample in a capillary tube.
Dry remote site blood spot sampling had its beginning in the 1960's with the use of filter paper to gather blood spot samples from neonates for use in the determination of the presence of phenylketones (Guthrie, et al., [1963
] Pediatrics
32(3): 338-343). Since that time, a number of products have been introduced that are designed to facilitate remote site sample collection and transport of the sample to a laboratory for analysis. The availability of remote site blood collection such that the collected sample can be transported to a laboratory for analysis has been very successful in monitoring blood components of diabetics.
Diabetes is a chronic and serious disease which affects over 100 million individuals worldwide. In the United States, there are 8 million diagnosed cases of diabetes, with an estimated 8 million cases undiagnosed. Diabetes is the leading cause of blindness, stroke, kidney failure, and amputations in the U.S. Because a person with diabetes is ten (10) times more likely to require hospitalization than the general population, the direct and indirect medical costs for treating diabetes have been estimated to exceed $105 billion annually. This total equals 14.6% of total U.S. healthcare expenditures being consumed by 3% of the population.
In about 1980, Schleicher and Schuell Corp. (S&S) began producing a filter paper attachable to a test request form (designed to order). In using the S&S system, a blood spot is placed in one or more designated areas of the filter paper, allowed to dry, and then mailed along with the test request form to the laboratory.
Eross, et al. introduced the use of filter paper spots for the gathering of blood spot samples for the measurement of glycohemoglobin. Eross, et al. (1984) Ann. Clin. Biochem. 21: 477-483. In 1986 Little, et al. reported on the use of filter paper blood spotting for measuring glycohemoglobin by affinity chromatography (Little, et al., [1986] Clin. Chem. 32(5): 869-871). Measurement of glycosylated hemoglobin (glycohemoglobin) or a component thereof, e.g., HbA1c, is extremely important in metabolic control of diabetics. Using the Little technology, Evalu-lab, a subsidiary of Awareness Technology, produced a product, Self-Assure™ (now owned by FlexSite Diagnostics), between 1987 and 1992 which gathered a blood spot sample on filter paper for glycohemoglobin or HbA1c determination. The blotting material used in these assays was a glucose oxidase-treated filter paper.
The methods and materials in this art have been the subject of many patents, including U.S. Pat. No. 5,516,487, which describes the use of various antibiotics or preservatives in combination with a cotton fiber filter paper, as well as the use of multiple application zones on the filter paper which are isolated from each other by perforations in the filter paper; U.S. Pat. No. 5,508,200, which describes the use of S&S 903 and S&S 470 filter papers in a complex integrated analytical system and measurement of chemical reactions on the filter paper matrix; U.S. Pat. No. 5,432,097, concerning digestion of the filter paper with cellulase so that recovery of intact cells can be achieved; U.S. Pat. No. 5,427,953, which concerns measurement of a heavy metal (e.g., lead) from blood samples collected on filter paper; U.S. Pat. No. 5,204,267, which describes preservation of blood samples collected on various filter matrices for glucose analysis; U.S. Pat. No. 4,816,224, which is directed to a multiple layer device for separating plasma or serum from a blood sample collected for glucose analysis; U.S. Pat. No. 4,299,812, pertaining to an improved thyroid function (T4) test; and U.S. Pat. No. 4,227,249, which primarily concerns a drying procedure and its effect on the results of an assay measuring somatomedin. The disclosures of these patents are hereby incorporated by reference.
Other patents describing the use of certain blotting materials used in biological assay methods include U.S. Pat. Nos. 5,496,626; 5,460,057; 5,415,758; 4,790,797; and 4,774,192. None of the above-referenced patents relate to the use of blotting materials used in association with a standard assay for hemoglobin (Hb) or hemoglobin A1c (HbA1c) or describe superior performance of the Hb or HbA1c assay by use of those materials.
In about 1992, Bio-Rad introduced a 100 test kit (wet samples) to facilitate the collection of capillary samples for analysis on their Diamat™ HPLC (High Performance Liquid Chromatography) system. Eli Lilly subsequently packaged a one test version of this kit as a promotional tool for their insulin products.
In Sweden about 1994 Boehringer Mannheim Corp. (BMC) introduced a mail-in, filter paper based (“dry”) blood spot kit under the name of “Via Post™” for HbA1c measurement. This BMC kit was evaluated by Jeppsson, et al. (Diabetes Care 19(2): pp. 142-145). BMC also introduced a “wet” capillary HbA1c kit for analysis on a Bio-Rad HPLC in 1995, and in 1996 introduced a screen material for blood spot sampling for analysis with their TinaQuant™ method for Hemoglobin A1c (Niederau, et al. [1996] Clin. Chem. 42(6): 167). Little, et al. ([1996] Clin. Chem. 42(6): 193) evaluated the use of filter paper for HbA1c sample collection with analysis by HPLC and by the Roche Unimate™ method. Voss, et al. evaluated capillary collection systems for HbAlc analyses. Diabetes Care (1992) 15: 700.
Historically, the most commonly used material for these assays has been S&S 903, a cotton linter paper. However, certain disadvantages have been associated with the S&S 903 paper and its equivalents available from other manufacturers, e.g., Whatman. Specifically, certain of these commercially available and commonly used materials lack characteristics which provide precision values and accuracy that is preferred for carrying out a commercially superior HbA1c assay.
Measurement of HbA1c, unlike blood glucose monitoring which provides an individual with their glucose value at that instant, measures the degree of diabetes control over the last 2-3 month period. In doing so, HbA1c monitoring provides the healthcare professional and patient a critical tool to determine the effectiveness of the patient's therapy and/or the patient's overall compliance.
Albeit recognized that HbA1c monitoring is beneficial, it is estimated that fewer than 16% of the 8 million individuals with diabetes have an A1c test annually, less than 10% have the test performed on a quarterly basis as recommended. The primary reasons for this is that a majority of patients with diabetes are treated by primary care physicians who are not current on the benefits of intensive therapy and HbA1c monitoring. Also, A1c testing has historically been an expensive laboratory test which required a blood draw by venipuncture which is poorly tolerated by both young and older patients.
Thus, discovery of unexpectedly improved or superior Hb or HbA1c assay results using materials that are commercially available and presumed to provide only equivalent results adds significantly to this art by improving the accuracy of detection of the blood components of inter
FlexSite Diagnostics, Inc.
Jones Deborah
McNeil Jennifer
Senterfitt Akerman
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