Method for the analysis of medical samples containing haemoglobin

• US 6,207,459 B1
• Filed: 11/20/1998
• Issued: 03/27/2001
• Est. Priority Date: 05/31/1996
• Status: Expired due to Term

• Current Assignee: Roche Diagnostics GmbH (Roche Holding AG)
• Original Assignee: Roche Diagnostics GmbH (Roche Holding AG)
• Inventors: Weisheit, Ralph, Schellong, Lieselotte
• Primary Examiner(s): Warden, Jill
• Assistant Examiner(s): TRAN, HUAN T
• Application Number:
  US09/147,288
• Time in Patent Office: 858 Days
• Field of Search: 436/66, 436/71, 436/86, 436/88, 436/84, 356/39
• US Class Current: 436/66
• CPC Class Codes: G01N 33/52 Use of compounds or compositions for colorimetric, spectrophotometric or fluorometric investigation, e.g. use of reagent paper and including single- and multilayer analytical elements immunological elements G01N33/54386; involving labelled immunochemicals G01N33/58; for haemoglobin or occult blood G01N33/72
• CPC Class Codes: G01N 33/6827 Total protein determination, e.g. albumin in urine
• CPC Class Codes: G01N 33/72 involving blood pigments, e.g. haemoglobin, bilirubin or other porphyrins; involving occult blood
• CPC Class Codes: G01N 33/84 involving inorganic compounds or pH

Abstract

The invention concerns a method for the determination of an analyte in a sample containing free haemoglobin in which the determination is carried out by an optical measurement and the value measured for the analyte concentration is mathematically corrected. This method is in particular suitable for determining the parameters total protein, iron and albumin in a medical sample e.g. in a serum or plasma sample. The correction of the measured value for the analyte concentration is achieved by the steps (a) measuring the blank value of the sample to be analysed, (b) measuring the blank value of a haemoglobin-free reference sample, (c) measuring the uncorrected value for the analyte concentration and (d) correcting the value obtained in step (c) by correlation with the values obtained in step (a) and (b) in order to obtain the corrected value for the analyte concentration.

Claims

1. A method for the determination of the concentration of an analyte in a sample containing free haemoglobin by optical measurement wherein the measured value for the analyte concentration is corrected by the steps:

a. optically measuring a blank value of the sample to be analyzed,

b. optically measuring a blank value of a haemoglobin-free reference sample,

c. adding a reagent to the sample to produce a detectable change in the sample indicative of analyte concentration,

d. optically measuring an uncorrected value for the analyte concentration and

e. correcting the uncorrected value obtained in step (d) by correlation with the blank values obtained in steps (a) and (b) in order to obtain a corrected value for the analyte concentration,

wherein the corrected value for the analyte concentration is calculated according to the following relation;

C′

_sample=C_sample−

F.E1_sample+F.E1_reference

in which C′

_sample is the corrected value for the analyte concentration,

C_sample is the uncorrected measured value for the analyte concentration in the sample,

F is a test-specific correction factor,

E1_sample is the measured blank value in the sample and E1_reference is the measured value in the reference sample.

2. Method as claimed in claim 1, wherein

the determination of the analyte is carried out by an optical measurement in the range of 600-700 nm.

3. Method as claimed in claim 1, wherein

the sample further comprises a blood substitute.

4. Method as claimed in claim 1, wherein

the total protein content of the sample is determined.

5. Method as claimed in claim 4, wherein

the determination of the total protein content is carried out according to the Biuret method.

6. Method as claimed in claim 1, wherein

the iron content of the sample is determined.

7. Method as claimed in claim 6, wherein

the iron content is determined according to the ferrozine method.

8. Method as claimed in claim 1, wherein

the albumin content of the sample is determined.

9. Method as claimed in claim 8, wherein

the albumin content is determined according to the bromocresol-green or the bromocresol-purple method.

10. Method as claimed in claim 1, wherein

in the determination of lipaemic samples and prior to step (a) in claim 1 a clearing agent is added.

11. Method as claimed in claim 1, wherein

the determination is carried out on a serum or plasma sample.

12. Method as claimed in claim 1, wherein

serum or plasma samples of clinically healthy test persons are used to produce the haemoglobin-free reference sample.

13. Method as claimed in claim 1, wherein

the method is carried out in an automated analyzer.

14. Method as claimed in claim 1, wherein

the determination of the test-specific correction factor F comprises the steps:

(i) Preparing a series of at least three standard samples with the same content of analyte of which at least one of the standard samples contains no haemoglobin and at least two of the standard samples contain different concentrations of free haemoglobin,

(ii) measuring a blank value of each standard sample to determine the increase of the standard sample blank value caused by the presence of haemoglobin compared to the haemoglobin-free standard sample,

(iii) measuring an uncorrected analyte concentration in each standard sample to determine the falsification of the measured value caused by the presence of haemoglobin compared to the haemoglobin-free standard sample and

(iv) the falsification of the measured value determined in step (iii) is correlated with the increase of the standard sample blank value determined in step

(iii) in order to obtain the test specific correction factor, F.

15. Method as claimed in claim 14, wherein

a series of standard samples is prepared of which at least 5 of the standard samples contain different concentrations of free haemoglobin.

16. Method as claimed in claim 14, wherein

a series of samples is prepared the concentration of which varies from 0 mg/dl to at least 1000 mg/dl of free haemoglobin.

17. Method as claimed in claim 14, wherein

a sample-specific correction factor F′

is determined for a sample containing free haemoglobin according to the following relationship;