EP1842047A1

EP1842047A1 - Method and device for spectroscopically examining body fluids and tissue samples with regard to an increased suspicion of alzheimer's disease

Info

Publication number: EP1842047A1
Application number: EP05803953A
Authority: EP
Inventors: Wolfgang Petrich; Joachim MÖCKS
Original assignee: F Hoffmann La Roche AG; Roche Diagnostics GmbH
Current assignee: F Hoffmann La Roche AG; Roche Diagnostics GmbH
Priority date: 2004-12-18
Filing date: 2005-11-12
Publication date: 2007-10-10
Also published as: US20080036999A1; DE102004061064A1; WO2006063644A1

Abstract

The invention relates to a method for spectroscopically examining samples which are taken from human tissue or body fluids, particularly blood, comprising the following steps: measuring an infrared spectrum of a sample to be examined; evaluating the measured infrared spectrum for determining at least one sample parameter that characterizes the infrared spectrum in at least one of the following wave number ranges 2850 cm-1 to 2886 cm-1, 2798 cm-1 to 2835 cm-1, 1723 cm-1 to 1733 cm-1, 1429 cm-1 to 1465 cm-1, 1338 cm-1 to 1364 cm-1, 1089 cm-1 to 1123 cm-1, 1034 cm-1 to 1074 cm-1; comparing the at least one sample parameter with at least one reference parameter that was obtained by evaluating at least one reference spectrum, which was measured on at least one sample of body fluid of patients stricken with Alzheimer's disease, and; assigning the sample to a class with an increased suspicion of Alzheimer's disease in the event the difference of the at least one sample parameter of the at least one reference parameter does not exceed a predetermined threshold value.

Description

Method and apparatus for spectroscopic

Examination of body fluids and tissue samples for increased Alzheimer suspensions

The invention relates to a method and a device for the spectroscopic examination of human tissue samples and body fluids, in particular blood, with regard to an increased Alzheimer suspected.

Alzheimer's is a widespread disease that is extremely difficult to diagnose, especially in its early stages. About 6% to 8% of people over the age of 65 have Alzheimer's disease. At the beginning, the symptoms of this disease are relatively mild and are often misconstrued as ordinary signs of aging. As the disease progresses, symptoms increase from mild forgetfulness to severe disruption of all cognitive functions of the brain. However, a definitive diagnosis of Alzheimer's is currently possible only post-mortem by histopathological examination of brain tissue.

The object of the invention is therefore to show a way how a physician early diagnosis of Alzheimer's can be facilitated. This object is achieved by a method for the spectroscopic examination of samples taken from human tissue or body fluids, in particular blood, comprising the following steps:

Measuring an infrared spectrum of a sample of the body fluid to be examined;

Evaluation of the measured infrared spectrum for determining at least one sample parameter, the infrared spectrum in at least one, preferably at least two, more preferably at least three, in particular at least four, of the following wavenumber ranges

2850 cm ^"1 to 2886 cm ^{" 1} , 2798 cm ^"1 to 2835 cm ^{" 1} ,

1723 cm " ¹ to 1733 cm" ¹ ,

1429 cm ^"1 to 1465 cm ^{" 1} ,

1338 cm ^"1 to 1364 cm" ¹ ,

1089 cm ^"1 to 1123 cm ^{" 1} , 1034 cm ^"1 to 1074 cm" ¹ , characterized

Comparing the at least one sample parameter with at least one reference parameter obtained by evaluating at least one reference spectrum measured on at least one sample of body fluid from Alzheimer's disease patients, _H and

Assignment of the sample to a class with increased Alzheimerverdacht, if the deviation of the at least one sample parameter of the at least one Reference parameter does not exceed a predetermined threshold.

The object is further achieved by a device for examining samples taken from human tissue or body fluids, in particular blood, comprising: a light source for emitting infrared light, a spectrometer for measuring an infrared spectrum of a sample of the body fluid to be examined, an evaluation unit which, during operation, determines at least one sample parameter by evaluating the measured infrared spectrum, which determines the infrared spectrum in at least one of the following number of wavelengths

2850 cm ^'1 to 2886 cm ^"1 ,

2798 cm ^'1 to 2835 cm ^"1 ,

1723 cm ^'1 to 1733 cm ^"1 ,

1429 cm ^"1 to 1465 cm ^'1 , 1338 cm ^{" 1} to 1364 cm ^"1 ,

1089 cm ^"1 to 1123 cm ^{" 1} ,

1034 cm ^"1 to 1074 cm ^{" 1} , which compares at least one sample parameter with at least one reference parameter obtained by evaluating at least one reference spectrum measured on at least one sample of body fluid from patients suffering from Alzheimer's; Assign sample to a class with elevated Alzheimer's Disease, if the deviation of the at least one Parameters of the at least one reference parameter does not exceed a predetermined value.

In another context, EP 0 644 412 A2 discloses a method for analyzing clinically relevant fluids with regard to liver cirrhosis or diabetes. The known method involves the following steps: a) Measurement of infrared spectra of a plurality of samples belonging to known classes, i. those from patients with diabetes or cirrhosis or healthy controls; b) carrying out a multivariate evaluation method with minimization of assignment errors of the samples to the known classes; c) storing the parameters obtained by minimization of the multivariate evaluation method; d) providing a sample to be examined, - e) placing the sample on a support; f) drying of the sample, - g) irradiation of the sample with infrared radiation; h) recording an infrared spectrum of the sample; i) analysis of the infrared spectrum by a multivariate evaluation method; j) Output of the assignment of the sample to a class of the multivariate evaluation method.

An overview of the use of infrared spectroscopic examinations in the field of medical diagnostics is provided by the article by W. Petrich in Applied Spectroscopy Reviews, 36 (2 & 3), 181-237 (2001). In the context of the present invention, it has been found that the method known from EP 0 644 412 A2 can also assist in the diagnosis of Alzheimer's disease by allowing samples of a class with an increased Alzheimer's suspicion to be assigned. With regard to the measuring technique and advantageously applicable multivariate evaluation method, reference is made to EP 0 644 412 A2, the disclosure of which is incorporated by reference into the subject of the present application.

In particular, it has been found within the scope of the invention that a sample of a class with an increased Alzheimer suspicion can be assigned with surprising reliability by determining a sample parameter which characterizes the infrared spectrum in at least one of the wave number ranges mentioned above.

Preferably, this sample parameter is obtained by a multivariate evaluation method, for example by discriminant analysis, cluster analysis or neural networks. The validity of the sample parameter is higher if several of the above wave number ranges, in particular the ranges of 1034 cm ^"1 to 1074 cm ^{" 1} , 1089 cm " ¹ to 1123 cm ^{" 1} and / or 2798 cm ^"1 to 2835 cm ^{" 1} in the evaluation is included so that the sample parameter characterizes the infrared spectrum in several wavenumber ranges.

In an evaluation, a sample spectrum can be represented by a point in a multidimensional parameter space. In the same way, a reference spectrum as a point, or a group of reference spectra as a point cloud, can be represented in the parameter space. The coordinates of the points characterizing the sample or reference spectra can be used as sample or reference parameters are understood. To put it clearly, the assignment of the sample to a class with an increased Alzheimer's suspicion can be based on the distance between points representing sample or reference spectra. However, it is not necessary that a distance be determined in the numerical sense. For example, the assignment can also take place by means of a neural network and it can only be ascertained that the corresponding spectra in the one or more spectral regions relevant to the invention are sufficiently similar for an assignment.

An increased Alzheimer's suspicion can be detected particularly reliably if the threshold value for the deviation of the sample parameter from the reference parameter is not given as an absolute value, but depends on the result of a comparison of the sample parameter with a second reference parameter. Similar to the first reference parameter characterizing one or more spectra measured on samples from patients with Alzheimer's disease, the second reference parameter characterizes spectra measured on samples from persons in a comparison group. For example, this comparison group can be people who are healthy. Another possibility is that the persons of the comparison group suffer from a dementia disease different from Alzheimer's, for example a vascular dementia. The symptoms of various dementias are often very similar, so that diagnosis can be very difficult even for experienced physicians. Difficult is often the distinction between Alzheimer's and other perceptive or memory disorders as well as mental illnesses, especially depression. Such diseases are in the English-language literature under the term "cognitive impairment" summarized. By applying the method according to the invention, a correct diagnosis can be made much easier for the physician even in such difficult cases.

Further details and advantages of the invention will be explained with reference to an embodiment with reference to the accompanying drawings. The features set forth herein may be used alone or in combination to provide preferred embodiments of the invention.

FIG. 1 shows an absorption spectrum of a blood sample of an Alzheimer's patient.

Figure 1 shows in the upper third of a typical absorption spectrum, which was measured on a dried sample blood serum of a patient with Alzheimer's disease. The intensity is plotted in arbitrary units over the wavenumber in cm ^-1 . Wavelength ranges which are particularly significant for the assignment of the sample to a class with an increased Alzheimer suspicion are indicated by solid bars in Figure 1. These particularly important wavenumber ranges are: 1034 cm -1. ¹ to 1074 cm ^"1 , 1089 cm ^{" 1} to 1123 cm " ¹ , 1338 cm ^{" 1} to 1364 cm " ¹ , 1429 cm" ¹ to 1475 cm ^"1 , 1723 cm ^{" 1} to 1733 cm ^"1 , 2798 cm ^{" 1} to 2835 cm ^"1 and 2850 cm" ¹ to 2886 cm ^"1 .

By using a multivariate evaluation method, for example, linear discriminant analysis or neural networks, a sample parameter was determined which characterizes the sample spectrum shown in the wavenumber range mentioned above. To decide whether to assign this sample to a class with elevated Alzheimer's Disease is, the sample parameter is compared with a reference parameter. The reference parameter characterizes in the wavenumber ranges mentioned reference spectra measured on samples of the body fluid of patients suffering from Alzheimer's. The reference parameter is determined as well as the sample parameter by using a multivariate evaluation method.

If several reference spectra are used, which is preferred, it is possible initially to determine a reference parameter separately for each reference spectrum and to determine the sample parameter with a value derived from the individual reference parameters, e.g. the mean, to compare. Another possibility is to determine from a plurality of measured reference spectra for the wave number ranges mentioned a characteristic general reference spectrum for which a single reference parameter is determined for comparison with the sample parameter.

If the deviation of the at least one sample parameter from the at least one reference parameter is below a predetermined threshold value, then the sample is assigned to a class with an increased Alzheimer suspicion.

Below the absorption spectrum, the Mann-Whitney score (MW score) is plotted in FIG. 1 for the respective wavenumber of the spectrum. The Mann-Whitney Score is a measure of the reliability of assigning the sample to a class of elevated Alzheimer's Disease, based solely on the respective wave number. In other words, the Mann-Whitney score indicates how characteristic the intensity of a spectrum is at a given wave number for Alzheimer's disease. As you can see, the Mann-Whitney score shows no strongly pronounced maxima, so that a reliable assignment of a sample spectrum to a class with increased Alzheimer suspicion at first sight seems hopeless. It is therefore all the more surprising that, on the basis of the marked wavenumber ranges, such an assignment is possible with such great reliability that a doctor can be given valuable help in the diagnosis of Alzheimer's. It is not even mandatory that all six specified wave number ranges are taken into account when determining the sample parameter.

In the lower third of FIG. 1, wavenumber ranges are marked by black bars which, when the multivariate is indicated by its abbreviation, is used

Evaluation method as an indication of Alzheimer's disease have proven.

The multivariate evaluation methods used are linear discriminant analysis LDA, robust linear discriminant analysis R-LDA, support vector machines SVM and neural networks ANN. As can be seen, the areas identified as characteristic by means of the various multivariate evaluation methods show considerable differences, which at first glance also makes a reliable assignment seem hopeless. On closer inspection, however, it can be seen that with the four multivariate evaluation methods given for some wavenumber ranges, an increased significance for the presence of Alzheimer's was consistently found. These areas are highlighted in Figure 1 by solid bars and are used in the described method to a sample, or a attributed infrared spectrum of a class with increased Alzheimer suspicion.

Claims

claims

1. A method for the spectroscopic examination of samples obtained from human tissue or body fluids, in particular blood, comprising the following steps:

Measuring an infrared spectrum of a sample to be examined;

Evaluation of the measured infrared spectrum for the determination of at least one sample parameter which determines the infrared spectrum in at least one of the following wavenumber ranges

2850 cm " ¹ to 2886 cm ^{" 1} ,

2798 cm ^"1 to 2835 cm ^{" 1} , 1723 cm ^"1 to 1733 cm ^{" 1} ,

1429 cm ^"1 to 1465 cm ^{" 1} ,

1338 cm ^"1 to 1364 cm ^{" 1} ,

1089 cm " ¹ to 1123 cm" ¹ ,

1034 cm ^"1 to 1074 cm" ¹ , characterized

Comparing the at least one sample parameter with at least one reference parameter obtained by evaluating at least one reference spectrum measured on at least one sample of body fluid of Alzheimer's disease patients, and Assignment of the sample to a class with increased Alzheimer suspected if the deviation of the at least one sample parameter from the at least one reference parameter does not exceed a predetermined threshold.

2. The method according to claim 1, characterized in that the predetermined threshold value depends on the result of a comparison of the sample parameter with a second reference parameter obtained by evaluation of one or more further reference spectra obtained on samples of body fluid from persons of a comparison group were measured.

3. The method according to claim 2, characterized in that the persons of the comparison group are healthy.

4. The method according to claim 2, characterized in that the persons of the comparison group suffering from a different dementia Alzheimer's disease, in particular a vascular dementia.

5. The method according to claim 2, characterized in that the persons of the comparison group suffer from a different from Alzheimer perception or memory disorder.

6. The method according to claim 2, characterized in that the persons of the comparison group suffer from a seeli- see illness, in particular a depression.

7. The method according to any one of the preceding claims, characterized in that the sample and reference parameters are determined by using a multivariate evaluation.

8. The method according to any one of the preceding claims, characterized in that the sample is obtained from blood.

9. The method according to any one of the preceding claims, characterized in that the sample is dried before the measurement.

10. The method according to any one of the preceding claims, characterized in that the infrared spectrum of the sample is measured with a Fourier spectrometer.

11. A device for the examination of samples obtained from human tissue or body fluids, in particular blood, comprising: a light source for emitting infrared light, a spectrometer for measuring an infrared spectrum of a sample of the body fluid to be examined, an evaluation unit, which in the Operation - determined by evaluation of the measured infrared spectrum at least one sample parameter, the infrared spectrum in at least one of the following wavenumber ranges

2850 cm ^"1 to 2886 cm ^{" 1} , 2798 cm ^"1 to 2835 cm ^{" 1} ,

1723 cm ^"1 to 1733 cm ^{" 1} ,

1429 cm ^"1 to 1465 cm ^{" 1} , 1338 cm ^"1 to 1364 cm ^{" 1} ,

1089 cm ^"1 to 1123 cm ^{" 1} ,

1034 cm ^"1 to 1074 cm ^{" 1} , which compares at least one sample parameter with at least one reference parameter obtained by evaluating at least one reference spectrum measured on at least one sample of body fluid from Alzheimer's disease patients, and the sample assigns a class with an increased Alzheimer suspected, if the deviation of the at least one sample parameter from the at least one reference parameter does not exceed a predetermined position lenwert.