# US 2014/0192342 A1 · Method and system for determining the concentration of substances in body fluids

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- Number: US 2014/0192342 A1
- Document ID: US20140192342A1
- Status: Published application
- Kind: A1
- Application number: 14/233,566
- Filed: 2012-07-16
- Published: 2014-07-10
- Earliest claimed: 2011-07-18
- Assignees: Siemens Healthcare Diagnostics Products GmbH
- Inventors: Karl Sass; Dirk Greis; Michael Noah; Christian Ueckermann
- Web page: https://patentgrep.com/patent/US20140192342A1

## CPC

- G01N 21/59: Transmissivity (G01N21/25 takes precedence)
- G01N 21/31: Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry {(G01N21/72 takes precedence)}
- G01N 21/314: {with comparison of measurements at specific and non-specific wavelengths (dual wavelength spectrometry G01J3/427)}
- G01N 33/491: {by separating the blood components (G01N15/05 takes precedence)}
- G01N 33/492: {Determining multiple analytes}
- G01N 2021/3129: {Determining multicomponents by multiwavelength light}
- G01N 2021/3148: {using three or more wavelengths}
- G01N 2201/129: Using chemometrical methods
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

The invention relates to a method for the spectrophotometric determination of the concentration of multiple substances, preferably bilirubin, haemoglobin and lipids, in a sample of body fluid.

## Claims

### Claim 1

A method for determining the concentrations of lipids and at least one further substance in a body fluid sample, comprising the steps of:
a) irradiating light through the body fluid sample at a multiplicity of wavelengths and
b) capturing a multiplicity of measured values of the absorbance of the body fluid sample at the multiplicity of wavelengths;
characterized by the steps of:
c) capturing a first measured value at a first wavelength at which the absorbance not caused by lipids is negligible, and determining the concentration of the lipids by dividing the measured value by the extinction coefficient specific for lipids;
d) calculating a power-function approximation curve of the form
E(λ)=p·λ−q
for the absorbance of the lipids on the basis of the first measured value by determining the factor p at predetermined exponent q;
e) determining a first approximate value of the concentration of the second substance on the basis of a second measured value and values of the approximation curve at a second wavelength.

### Claim 2 (depends on 1)

The method as claimed in claim 1, comprising the steps of:
f) calculating an absorbance value at a third wavelength on the basis of the first approximate value and values of the approximation curve;
g) ascertaining a deviation of the calculated absorbance value from a third measured value at the third wavelength;
h) correcting the approximation curve on the basis of the ascertained deviation; and
i) determining the concentration of the second substance (H) by correcting the first approximate value on the basis of the second measured value and values of the corrected approximation curve.

### Claim 3 (depends on 2)

The method as claimed in claim 2, wherein a third substance in the body fluid sample is additionally determined, additionally comprising the steps of:
j) determining a second approximate value of the concentration of the third substance on the basis of the second measured value and values of the approximation curve at the second wavelength and also of a fourth measured value and values of the approximation curve at a fourth wavelength; and
k) determining the concentration of the third substance by correcting the second approximate value on the basis of the second measured value, the fourth measured value and values of the corrected approximation curve, wherein the absorbance value is additionally calculated on the basis of the second approximate value.

### Claim 4 (depends on 3)

The method as claimed in claim 3, wherein the steps of calculating the absorbance value, of ascertaining the deviation, and of correcting the approximation curve, the first approximate value and the second approximate value are iterated until the deviation is below a predetermined threshold.

### Claim 5 (depends on 4)

The method as claimed in claim 4, wherein the second substance comprises hemoglobin and the third substance comprises bilirubin.

### Claim 6 (depends on 3)

The method as claimed in claim 3, wherein the first wavelength is within the range between 610 nm and 650 nm, the second wavelength is within the range between 410 nm and 420 nm, the third wavelength is within the range between 360 nm and 370 nm, and the fourth wavelength is within the range between 465 nm and 475 nm.

### Claim 7 (depends on 4)

The method as claimed in claim 4, wherein the predetermined threshold is 10 mE.

### Claim 8 (depends on 2)

The method as claimed in claim 2, wherein the approximation curve is corrected in such a way that the first measured value lies on the approximation curve.

### Claim 9 (depends on 1)

The method as claimed in claim 1, wherein irradiation through the body fluid sample is achieved using laser or light-emitting diodes and the multiplicity of measured values is captured using a photometric sensor.

### Claim 10

A system for determining the concentrations of substances in a body fluid sample, comprising:
i. a measurement device designed for irradiating light beams having a multiplicity of wavelengths through a body fluid sample, and for capturing a multiplicity of measured values of the absorbance of the body fluid sample at the multiplicity of wavelengths; and
ii. a calculation device designed for calculating a power-function approximation curve of the form
E(λ)=p·λ−q
for the absorbance of the lipids on the basis of a first measured value by determining the factor p at predetermined exponent q at a first wavelength at which the absorbance not caused by lipids is negligible, and for determining a first approximate value of the concentration of a second substance on the basis of a second measured value and values of the approximation curve at a second wavelength.

### Claim 11 (depends on 10)

The system as claimed in claim 10, wherein the calculation device is designed for calculating an absorbance value at a third wavelength on the basis of the first approximate value and values of the approximation curve, for ascertaining a deviation of the calculated absorbance value from a third measured value at the third wavelength, for correcting the approximation curve on the basis of the ascertained deviation, and for correcting the first approximate value on the basis of the second measured value and values of the corrected approximation curve.

### Claim 12 (depends on 11)

The system as claimed in claim 11, wherein the measurement device comprises laser or light-emitting diodes and a photometric sensor device.

### Claim 13 (depends on 11)

The system as claimed in claim 11, wherein the calculation device is additionally designed for determining a second approximate value of the concentration of a third substance on the basis of the second measured value and values of the approximation curve at a second wavelength and also of a fourth measured value and values of the approximation curve at a fourth wavelength, and for correcting the second approximate value on the basis of the second measured value and values of the corrected approximation curve, wherein the absorbance value is additionally calculated on the basis of the second approximate value.

### Claim 14 (depends on 13)

The system as claimed in claim 13, wherein the body fluid sample comprises blood serum or blood plasma, the second substance comprises hemoglobin and the third substance comprises bilirubin.

### Claim 15 (depends on 13)

The system as claimed in claim 13, wherein the first wavelength is within the range between 610 nm and 650 nm, the second wavelength is within the range between 410 nm and 420 nm, the third wavelength is within the range between 360 nm and 370 nm, and the fourth wavelength is within the range between 465 nm and 475 nm.