Chemistry: analytical and immunological testing – Composition for standardization – calibration – simulation,...
Reexamination Certificate
1999-07-15
2001-03-06
Wallenhorst, Maureen M. (Department: 1743)
Chemistry: analytical and immunological testing
Composition for standardization, calibration, simulation,...
C436S174000, C436S175000, C436S177000
Reexamination Certificate
active
06197592
ABSTRACT:
BACKGROUND OF THE INVENTION
Osteoporosis, or bone loss, is a condition that accompanies aging as well as a variety of diseases of diverse etiology. These diseases include metabolic bone diseases, hypogonadism, hyperadrenocorticism, scurvy, heritable disorders of connective tissue such as osteogenesis imperfecta, homocystinuria, and Ehlers-Danlos syndrome, and other conditions such as rheumatoid arthritis and idiopathic osteoporosis. Age-related osteoporosis is particularly prevalent among post-menopausal women.
If detected early, osteoporosis can be treated by nutritional supplements, hormone replacement therapy, and certain prescription drugs. Unfortunately, osteoporosis is not readily identifiable by physical examination, and often remains undetected until a bone fracture occurs causing the individual to suffer pain, and possible deformity and disability. As one gets older, the ability to respond to these treatments diminishes, and the complications become more serious. Thus, early detection is an important means of lessening or preventing the consequences of osteoporosis, and improving the quality of life for those who are susceptible to this condition.
Osteoporosis is detectable by a variety of methods. These include x-ray absorptiometry by single-energy, dual-energy and peripheral means, radiographic absorptiometry, quantitative computed tomography, quantitative ultrasound, bone densitometry, and the chemical analysis of urine samples. The most convenient and cost-effective method is the chemical analysis of a urine sample to detect the levels of certain biochemical markers of bone turnover. The higher the rate of resorption relative to the rate of formation of bone tissue, the greater the rate of bone loss. The level of resorption in particular is readily determined on a quantitative basis by the analysis of urine for breakdown products of bone mineral and matrix. These breakdown products, or markers, are the collagen crosslinks pyridinoline and deoxypyridinoline, and the type I collagen breakdown products N-telopeptide and C-telopeptide.
Assays of urine for these markers is done by high-performance liquid chromatography (HPLC) and by immunoassays. These immunoassays can be performed on automated equipment for enhanced efficiency and to permit the analysis of large numbers of samples. As with any clinical analysis, quality control requires that precision and accuracy be maintained in the performance of the test and the analysis of the test results. For this reason, the use of control materials, which contain known amounts of the markers, is an important component of the laboratory protocol. Unfortunately, the isolation and purification of the markers from urine, either normal urine or urine having an elevated level of the markers, is a tedious and cumbersome process, and for this reason the controls for these markers are very expensive, and at times prohibitively so. A further disadvantage of controls prepared in this manner is that they are primarily buffer solutions in which the markers are dissolved, and buffer solutions differ substantially from the patient's urine sample. This affects the analytical procedures and detracts from the ability to make direct comparisons between the controls and the test samples.
SUMMARY OF THE INVENTION
It has now been discovered that liquid controls for determinations of the four biochemical markers of osteoporosis in urine can be made by using urine-based materials that have been purified primarily by lyophilization and reconstitution, without the use of chromatographic means to extract the markers and separate them from other species present in urine. The urine-based materials may be derived either from normal urine or from urine with elevated levels of the markers. Lyophilization and reconstitution, together with the removal of extraneous substances that precipitate and do not redissolve, produce a clarified quantity of urine and, surprisingly, do so without loss or destruction of the markers present in the urine. The amount of each marker present in the starting urine is thus retained through the processing. Reconstitution with water produces a control solution whose matrix is clear yet highly similar to the patient's sample urine. The marker concentration can be controlled by the proportion of water used for reconstitution, and two or more aliquots can be combined to achieve any particular combination of the markers at target concentrations. The invention thus provides controls that are sufficiently clear to be suitable for use, that are sufficiently stable to be clinically useful, and that contain the markers in precisely known concentrations, and yet are inexpensive and easy to prepare while offering the added advantage of a matrix that is highly similar to those of the test samples. These qualities enable the control materials of this invention to facilitate reliable and accurate quantitation of samples of urine.
These and other features, objects, and advantages of the invention will be more readily understandable from the description that follows.
DESCRIPTION OF THE SPECIFIC EMBODIMENTS
This invention is directed to control materials for bone resorption marker determinations in urine samples and methods for their preparation of such control materials. The invention extends to control materials that contain only one of the four markers—pyridinoline, deoxypyridinoline, N-telopeptide, and C-telopeptide—and it also extends to control materials that contain two or more of these markers in combination, including control materials that contain all four. The choice of marker(s) for a particular control material will be governed by the marker whose presence is to be determined and quantified. The choice of marker(s) will vary with the preference or intentions of the manufacturer of the assay with which the control material(s) are to be used, the assay protocol itself, and the preference of the individual user. The materials of this invention may be used as controls, as well as calibrators and standards that contain the designated markers in known concentrations.
The terms “N-telopeptide” and “C-telopeptide” are used herein in the manner in which they are used by biochemists, to refer to sequences of about 12 to 25 amino acids that occur at the N- and C-terminals of the tropocollagen molecule. The terms “N-telopeptide” and “C-telopeptide” each refer to a class of species and each generally includes a mixture of species, including crosslinked species, within the class rather than a single species. Nevertheless, the presence and significance of N-telopeptide and C-telopeptide in urine for diagnoses of osteoporosis, as well as the meanings of the terms, are well recognized in the medical community. In this specification, C-telopeptide is represented by the abbreviation “CTX” and N-telopeptide by the abbreviation “NTX.” Due to its heterogeneity, NTX is expressed in terms of “bone collagen equivalents” (“BCE”), a term that is likewise recognized among practitioners who diagnose and treat osteoporosis. To compensate for the variations in urine concentrations that normally occur in a donor over the span of a typical day, the measured levels of CTX and NTX are normalized with respect to creatinine. Creatinine is selected for this purpose since it is expelled into the urine at a substantially constant rate. Its concentration in urine is thus a direct indication of the normal variations in urine concentrations occurring over the course of a day, and is therefore an appropriate normalizing factor. The CTX and NTX levels are thus expressed as &mgr;g/L per mM creatinine and nM BCE per mM creatinine, respectively.
The terms “peptide-free pyridinoline” and “peptide-free deoxypyridinoline” refer to proteolytically decomposed species, while “pyridinoline” and “deoxypyridinoline” each refer to a mixture of species which may retain attached protein. HPLC assays tend to read total pyridinoline and total deoxypyridinoline while immunoassays tend to read total pyridinoline and total deoxypyridinoline up to a certain maximum fragment length, typica
Duffy Thomas H.
Onishi Hanh
Bio-Rad Laboratories, Inc.
Townsend and Townsend / and Crew LLP
Wallenhorst Maureen M.
LandOfFree
Clinical control materials for detection of bone resorptive... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Clinical control materials for detection of bone resorptive..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Clinical control materials for detection of bone resorptive... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2528843