Method for calibrating spectrophotometric apparatus with synthetic fluids to measure plasma and serum analytes

• US 6,470,279 B1
• Filed: 11/23/1999
• Issued: 10/22/2002
• Est. Priority Date: 11/23/1999
• Status: Expired due to Fees

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: James Samsoondar
• Inventors: Samsoondar, James
• Primary Examiner(s): ASSOUAD, PATRICK J
• Application Number:
  US09/447,215
• Time in Patent Office: 1,064 Days
• Field of Search: 356/39, 356/40, 356/42, 702/22, 702/28, 702/85, 702/104, 702/30, 702/32
• US Class Current: 702/28
• CPC Class Codes: G01N 21/274 Calibration, base line adjustment, drift correction
• CPC Class Codes: G01N 21/4785 Standardising light scatter apparatus; Standards therefor

Abstract

Described is a method for calibrating a spectrophotometric apparatus which is used to measure analytes in plasma and/or serum samples based on the calibration of a First Apparatus, and for recalibrating such apparatus, including recalibration of the First Apparatus all using synthetic calibrators. These apparatus use absorption of radiation to measure analytes in serum or plasma samples. The method described includes using synthetic calibrators which are submitted to the First Apparatus for measurement and compared with measurements of similar calibrators in a Second Apparatus and using the comparison to derive concentrations of analytes in samples measured on the Second Apparatus. As an alternative to making all apparatus identical, in terms of wavelength calibration, the absorbances of all apparatus should be mapped onto a standard set of wavelengths.

Claims

1. A method for transferring a calibration algorithm from a First Apparatus to a Second Apparatus comprising:

(i) conducting a Primary Calibration of the First Apparatus to obtain at least one Primary Calibration Algorithm using a standard set of wavelengths;

(ii) obtaining measurements of absorbance of a set of calibrators on the First Apparatus for at least one wavelength from the standard set of wavelengths;

(iii) obtaining absorbance measurements of the set of calibrators on a Second Apparatus for at least one wavelength from the standard set of wavelengths;

(iv) establishing a linear regression equation for at least one wavelength from the standard set of wavelengths using the absorbance measurements from the First Apparatus and the Second Apparatus; and

(v) incorporating the at least one Primary Calibration Algorithm on the Second Apparatus.

2. A method of determining the concentration of an analyte in a sample in a Second Apparatus comprising:

(i) transferring a calibration algorithm from a First Apparatus according to the method of claim 1;

(ii) in the Second Apparatus measuring the absorbance of the sample for at least one wavelength from the standard set of wavelengths;

(iii) adjusting the measurements of absorbance from the sample with the linear regression equation for each of the at least one wavelength to obtain a corrected absorbance; and

(iv) calculating a concentration for the analyte using the corrected absorbance.

3. A method according to claim 2 wherein the Primary Calibration Algorithms and the calibration absorbance measurements on the First Apparatus are electronically stored and installed on the Second Apparatus.

4. A method according to claim 3 wherein the Primary Calibration Algorithms and the calibration absorbance measurements at the standard set of wavelengths on the First Apparatus are stored on a floppy diskette or an EPROM.

5. A method according to claim 2 wherein the samples used for the Primary Calibration are in a first type of vessel and the calibrators are in the same type of vessel.

6. A method according to claim 5 wherein the first type of vessel is a pipette tip, test tube (labelled or unlabelled), or blood bag tubing.

7. A method according to claim 6 wherein four calibrators are used.

8. A method according to claim 7 wherein the calibrators are all from the same batch.

9. A method according to claim 7 wherein the calibrators are exactly the same calibrators used to provide the absorbance measurement on the First Apparatus.

10. A method according to claim 8 wherein the calibrators mimic hemoglobin, bilirubin, turbidity or biliverdin.

11. A method according to claim 2 wherein the standard wavelengths are measured in the near infrared and adjacent visible light spectrum.

12. A method according to claim 11 wherein ten absorbance measurements are taken at each wavelength of the standard wavelength set.

13. A method for recalibrating a First Apparatus, a Second Apparatus, or both a First and Second Apparatus having a primary calibration algorithm comprising:

i) incorporating in the First, Second, or both the First and the Second Apparatus absorbance measurements for at least one wavelength of a set of calibrators to produce incorporated calibrators absorbance measurements;

(ii) obtaining measurements of absorbance of a similar set of calibrators on the First, Second, or both First and Second Apparatus for at least one wavelength from the standard set of wavelengths; and

(iii) establishing a linear regression equation for at least one wavelength from the standard set of wavelengths using the incorporated calibrators absorbance measurements and the measurements of absorbance of the similar set of calibrators obtained on the First, Second, or both First and Second Apparatus.

14. A method of determining the concentration of an analyte in a sample in an apparatus recalibrated according to the method of claim 13, comprising:

(i) measuring the absorbance of the sample in the recalibrated apparatus for at least one wavelength from the standard set of wavelengths;

(ii) adjusting the measurements of absorbance from the sample with the linear regression equation for each of the at least one wavelength to obtain a corrected absorbance; and

(iii) calculating a concentration for the analyte using the corrected absorbance.

15. A method according to claim 14 wherein the samples used for the Primary Calibration are in a first type of vessel and the calibrators are in the same type of vessel.

16. A method according to claim 15 wherein the first type of vessel is a pipette tip, test tube (labelled or unlabelled), or blood bag tubing.

17. A method according to claim 14 wherein four calibrators are used.

18. A method according to claim 17 wherein the calibrators are all from the same batch.

19. A method according to claim 18 wherein the calibrators mimic hemoglobin, bilirubin, turbidity or biliverdin.

20. A method according to claim 14 wherein the standard wavelengths are measured in the near infrared and adjacent visible light spectrum.

21. A method according to claim 20 wherein ten absorbance measurements are taken at each wavelength of the standard wavelength set.

22. A method of determining the concentration of an interferent in a sample in a Second Apparatus using a calibration algorithm from a First Apparatus comprising:

(i) conducting a Primary Calibration of the First Apparatus to obtain at least one Primary Calibration Algorithm using a standard set of wavelengths in the near infrared and adjacent visible range and storing the at least one Primary Calibration Algorithm in a calibration information package;

(ii) obtaining calibrators'"'"' absorbance measurements of a set of calibrators for at least one wavelength from the standard set of wavelengths on said First Apparatus and storing the calibrators '"'"' absorbance measurements in a calibration information package;

(iii) installing the calibrators'"'"' absorbance measurements and the at least one Primary Calibration Algorithms stored in a calibration information package in the Second Apparatus;

(iv) obtaining measurements of absorbance of the set of calibrators on a Second Apparatus for at least one wavelength from the standard set of wavelengths;

(v) establishing a linear regression equation for each of the at least one wavelength from the standard set of wavelengths using the calibration absorbance measurements from the First Apparatus and the measurements of absorbance from the Second Apparatus and electronically storing the linear regression equation in the Second Apparatus;

(vi) measuring the absorbance of the sample for at least one wavelengths from the standard set of wavelengths in the Second Apparatus;

(vii) adjusting the measurements of absorbance from the sample with the First linear regression equation for each of the at least one wavelength to obtain a corrected absorbance; and

(viii) calculating a concentration for the analyte using the corrected absorbance.

23. A method of determining the concentration of an analyte in a sample in a Second Apparatus comprising:

(i) conducting a Primary Calibration of a First Apparatus to obtain at least one Primary Calibration Algorithm using a standard set of wavelengths, and incorporating the at least one Primary Calibration Algorithm on the Second Apparatus;

(ii) measuring the absorbance of the sample for at least two wavelengths from the standard set of wavelengths in the Second Apparatus;

(iii) obtaining a mathematical derivative of the measured absorbance from step (ii); and

(iv) calculating a concentration for the analyte using the derivative of absorbance measurement.

24. A method according to claim 23 wherein the derivative of the measured absorbance is chosen from at least one of the first, second, or third derivatives.