Optics: measuring and testing – Blood analysis – Hemoglobin concentration
Reexamination Certificate
1997-06-09
2002-03-05
Hantis, K. P. (Department: 2876)
Optics: measuring and testing
Blood analysis
Hemoglobin concentration
Reexamination Certificate
active
06353471
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to spectrophotometry and the spectrophotometric analysis of blood samples. In particular, this invention relates to a method and apparatus for providing a non-destructive pre-test screen of specimen integrity for a blood analyzer by measurement of absorbance or reflectance.
BACKGROUND OF THE INVENTION
Clinical laboratory tests are routinely performed on the serum or plasma of whole blood. In a routine assay, red blood cells are separated from plasma by centrifugation, or red blood cells and various plasma proteins are separated from serum by clotting prior to centrifugation.
Haemoglobin (Hb), bilirubin (Bili) and light-scattering substances like lipid particles are typical substances which will interfere with, and affect spectrophotometric and other blood analytical measurements. Such substances are referred to as interferents. Elevated Bili can be due to disease states, and increased lipid particles in the blood, also known as hyperlipidemia, can be due to disease states and dietary conditions. Elevated Hb in the blood, hemoglobinemia, can be due to disease states and as a result of specimen handling. Clinical laboratories currently emphasize these three potential interferents as being of greatest concern with respect to affecting blood analysis. Biliverdin, (BV), a fourth potential interferent, is rarely mentioned.
BV is the precursor of Bili, and if Bili becomes oxidized, it will revert to BV. BV and Bili are two of a class of compounds referred to as bile pigments. BV is not normally present in serum, but regularly accompanies Bili in the serum of patients with carcinomatous obstruction of the bile duct, and is frequently found in the blood of patients with liver cirrhosis, and bile duct occlusion by gallstones.
Upon visual inspection, Bili gives a yellow or orange colour to serum and 10 plasma and is considered to be the major bile pigment in serum or plasma. Bili is sometimes described as a greenish/yellow pigment (Guyton, A. C. and Hall, J. E., Textbook of Medical Physiology, 1996, page 886). However, it is likely BV, rather than Bili, that is responsible for the greenish colour. In fact, these specimens may, nevertheless, have acceptable levels of Bili. A yellow colour chart is available for visual grading of Bili levels in serum or plasma, but there is no known colour chart for green bile pigment or BV. Visual inspection may still provide any opportunity for rejection of green specimens, however, for automated systems, no method exists for screening serum or plasma specimens for increased blood levels of BV, also known as hyperbiliverdinemia.
Many tests conducted on plasma or serum samples employ a series of reactions which terminate after the generation of chromophores which facilitate detection by spectrophotometric measurements at one or two wavelengths. Measurement of interfering substances prior to conducting such tests is important in providing meaningful and accurate test results. In fact if a sample is sufficiently contaminated with interferents, tests are normally not conducted as the results will not be reliable.
Specimen integrity is an essential part of quality assurance as it directly affects the accuracy of test results. The presence of interferents in a plasma or serum sample compromises specimen integrity.
Spectrophotometric measurement uses infrared (IR) or near infrared radiation (NIR) to assess the concentration of various constituents in a blood sample. Examples of photometric measurements using containers which hold a blood sample are disclosed in U.S. Pat. Nos. 5,291,884; 5,288,646; 5,066,859; and 5,366,903.
U.S. Pat. No. 5,366,903 discloses a sampling device which allows photometric quantitative determination of an analyte in whole blood. The device overcomes the problems of having blood cells in a blood sample by effectively “squeezing out” red blood cells and providing a small volume of sample, free of red blood cell material, from which particular analytes can be measured.
Other applications of photometric methodology include non-invasive determinations of analyte concentrations such as described in U.S. Pat. Nos. 5,360,004; 5,353,790; and 5,351,685. However none of these documents discloses a method of measuring interferents in the plasma or serum of a blood sample, in order to assess specimen integrity for further analysis.
Current methods used for detecting haemoglobinemia, bilirubinemia and lipemia or turbidity utilize visual inspection of the specimen with or without comparison to a coloured chart. It is to be understood that those practising in the field use the terms lipemia and turbidity interchangeably. This is so because lipemia is the major cause of turbidity in serum or plasma.
Visual inspection is sometimes employed on a retrospective basis where there is a disagreement between test results and clinical status of the patient in order to help explain such discrepancies.
A sample of plasma or serum is normally transferred from an original or primary tube or container to a secondary tube or container. These secondary tubes are amber coloured to protect photo sensitive constituents. The amber colouring makes visual inspection virtually impossible. On occasion, labels cover portions of the tube further restricting a full visual examination.
Pre-test screening of specimens by visual inspection is semi-quantitative at best, and highly subjective and may not provide sufficient quality assurance as required for some tests.
Furthermore, visual inspection of specimens is a time consuming, rate limiting process. Consequently, state-of-the-art blood analyzers in fully and semi-automated laboratories do not employ visual inspection of specimens.
Other methods to assess specimen integrity employ direct spectrophotometric measurement of a diluted sample in a special cuvette. However, such methods are not rapid enough for screening samples. In order to obtain a measurement of the sample of the plasma or serum, primary specimen tubes, or containers, must be uncapped, a direct sample of the specimen taken and diluted prior to measurement. Both of these steps are time consuming and require specialized and/or disposable cuvettes.
SUMMARY OF THE INVENTION
It is desirable to provide an apparatus and a method whereby specimen integrity is rapidly and accurately assessed without disturbing the sample. The disadvantages of the prior art may be overcome by providing a rapid and accurate method and apparatus for monitoring blood specimen integrity before samples are presented for analysis.
In one aspect of the invention, spectral data is used in a novel way so as to determine if the specimen which is presented for such analysis in a primary container contains interferents and if so, to what extent.
In another aspect of the invention, there is provided an apparatus and a method for determining blood specimen integrity of a specimen contained in a primary container using a spectrophotometer to irradiate and measure radiation from the specimen.
In a further aspect of the invention, there is provided an apparatus and a method for determining blood specimen integrity, where a primary sample tube containing a specimen has a sample identification label on the exterior surface of the sample tube, by using a spectrophotometer to irradiate and measure radiation from the specimen.
In yet another aspect of the invention there is provided an apparatus and a method for determining blood specimen integrity of a specimen contained in a primary container where light is transmitted through the label, container and specimen.
In yet a further aspect of the invention, there is provided an apparatus and a method for determining blood specimen integrity of a specimen contained in a primary container, where the light is reflected from the backside of a label after penetrating the specimen and container through an unlabelled section of the container.
In another aspect of the invention, specimen integrity of a specimen contained in a primary container is assessed by measuring:
1. Haemoglobin concentration as an assessment of haemolysis;
Jacobs Merrit Nyles
Samsoondar James
CME Telemetrix Inc.
Hantis K. P.
Katten Muchin & Zavis
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