Chemistry: analytical and immunological testing – Biological cellular material tested
Reexamination Certificate
1993-08-12
2001-02-27
Wallenhorst, Maureen M. (Department: 1743)
Chemistry: analytical and immunological testing
Biological cellular material tested
C436S064000, C436S150000, C436S161000, C073S061520
Reexamination Certificate
active
06194217
ABSTRACT:
This invention relates to analytical and mathematical methods for diagnosing or categorizing disorders. The invention has particular utility for diagnosing or categorizing disorders in living animals from analysis profiles of biologically active materials such as neurotransmitters and other neurochemical substances in brain tissue, cerebrospinal fluid, plasma, serum, saliva, nasal mucosa, urine and the like, such as catecholamines, their precursors, cofactors and their metabolites. The invention is uniquely capable of differentiating a large number of compounds of biological, diagnostic and/or pharmaceutical significance and of using such differential for diagnosing disorders and will be described in connection with such utility although other uses are contemplated.
There is an extensive body of literature relating abnormalities in neurotransmitters, precursors, and metabolites to degenerative, neuropsychiatric and behavioral disorders, hypertension and certain carcinomas. See, for example, Schildkraut et al in
The Brain, Biochemistry and Behavior
, Proceedings of the Sixth, Arnold O. Beckman Conference in Clinical Chemistry, pages 47-68. Although the potential role of these compounds in a number of significant disorders has been established, their routine analysis has not yet achieved widespread clinical use. Two problems in the clinical utility of neurotransmitter measurements are related to the economic and technical limitations of current technology. First, there is felt to be a high degree of interlaboratory and intersample uncertainty in quantitative values. Second, it has been difficult to measure enough of the known metabolically related compounds of a particular neurotransmitter to fully describe its biochemical significance in an individual sample, or to detect, identify and measure unusual neurotransmitters—an important aspect of basic research in various disease states that is presently very expensive and specialized.
While a number of interlaboratory technique intercomparisons for a variety of neurotransmitters have been carried out, there has been no comprehensive study within and among different techniques and laboratories for neurotransmitters in typical samples of interest. In the absence of such studies, given the complexity of the analytical problem and the historically wide variation whenever an analyte has been subjected to rigorous interlaboratory testing, the current values for normal and abnormal neurotransmitter levels must be taken with unspecified and probably wide limits of confidence.
Although the analysis of single neurotransmitters or metabolites from a complex biochemical pathway has been shown to correlate with a number of disorders utilizing statistical analysis over a larger number of samples, the analytical level of a single neurotransmitter in an individual sample, with a few exceptions, has had relatively low clinical diagnostic utility. Essentially the state of the field of biochemical correlates of disorders is that while between large populations of normal and abnormal individuals a correlation generally can be determined for a particular biochemical, the scatter that results from both analytical and biochemical phenomena typically does not permit the level of a particular biochemical to be utilized diagnostically for a particular single individual. Nor may a single biochemical value be utilized for the rational prescription or development of a pharmaceutical for that individual. This is not particularly surprising in that both the levels and effects of a particular neurotransmitter are modified by a number of other neurotransmitters, in the same, or parallel metabolic pathways. If, for instance, 5-HT (serotonin) is to be used as a diagnostic tool for depression, suicidal tendencies, or schizophrenia, it would be necessary and perhaps provide a route to definitive diagnosis and pharmaceutical specification or development, to simultaneously determine the approximately 40 other compounds that derive from tryptophan and significantly effect the indolaminergic neuronal system's activity.
In recent years, LCEC (Liquid Chromatography with Electrochemical Detection) has become a common tool for the determination of catacholamines biogenic amines and their metabolites in biological fluids. Because of sensitivity limitations (typically 20-50 pg) and the complexity of biological samples, both separation and concentration steps typically have been necessary. Heretofore, plasma catecholamine analysis typically required three steps. First, the sample is collected and the catecholamines separated and concentrated, for example, using the alumina extraction procedure of Anton and Sayre (See A. H. Anton and D. F. Sayre, J. Pharmacol, Exp. Ther., 138 (1962), p. 360-375). The analytes, norepinephrine, epinephrine and donamine, along with the internal standard DHBH (dihydroxybenzylamine), then are separated chromatographically, and finally detected electrochemically. Typical sample size requirements are 1.0 ml plasma or serum. In routine clinical use, there have been numerous problems with conventional techniques (alumina absorption, ion exchange and extraction), due to a large number of poorly understood variables, in the overall analysis system of sample acquisition, storage, preparation and sensor response. These problems have quite likely confused the relationships that may exist between levels and distribution of the catecholamines and various physiological and behavioral phenomena and disease states.
In the analysis of complex biological materials such as blood, serum and cerebrospinal fluids which may contain numerous different constituents, the important (e.g. abnormal) metabolites such as neurotransmitters to be identified may be present in only parts per trillion. While a chromatographic column can achieve macro separation of the various constituents, it may not provide adequate spatial (in time) separation of the extremely small portion of metabolites of interest from the much larger percentage of the many other compounds coeluted from the column at the same time as the metabolites of interest. Many of these interfering coeluted materials are electrochemically active but electrochemically irreversible, while many metabolites such as neurotransmitters are both electrochemically active and electrochemically reversible. It has been found that the analytical problems of reliable measurements of neurochemicals and related compounds are complicated by the fact that interferences with conventional or prior technologies are disorder related. This was discussed in my prior publication, (Matson et al. Clinical Chemistry, Vol. 30, No. 9, 1984) (see U.S. Pat. No. 4,511,659) for dopamine, dopac and seratonin measurements in directly analyzed brain extract and cerebrospinal fluid for normal, schizophrenics and Alzheimers. Recent work has indicated that even for the widely used and accepted technique of alumina extraction for plasma catecholamines that interferences may be disorder specific. Higher values for Norepinephrine (NE) and Epinephrine (EP) were observed following alumina extraction and analysis of a single energy conventional electrochemical detector than for a three cell redox detector on neonatal stress blood samples. Analysis of the neonate extracts on the sixteen channel chemical imaging system revealed several unexpected compounds that are potential interferences including dihydroxyphenylacetic acid (DOPAC), 3 hydroxykynurenamine (3-OHKYA) and 3-hydroxy-anthranilic acid (3-OHAN). These compounds have not been detected in normal adult plasma alumina extracts.
In my aforesaid U.S. Pat. No. 4,511,659, there is provided an electrochemical detection system comprising a plurality of coulometrically efficient electrochemical cells, in series, for sequentially oxidizing and reducing selected substances in a sample solution under controlled conditions prior to measurement on a downstream testing electrode or electrodes. More specifically, in accordance with the invention provided in my aforesaid U.S. Pat. No. 4,51,659, a sample solution (e.g. a bo
Esa Inc.
Hayes, Soloway, Hennessey Grossman & Hage, P.C.
Wallenhorst Maureen M.
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