Quantitative computer image analysis of a human chorionic gonadotropin colloidal carbon dipstick assay

Clin Chim Acta. 1994 Sep;229(1-2):67-75. doi: 10.1016/0009-8981(94)90229-1.


Colloidal particles are widely used in qualitative dipstick assays for the determination of various proteins and haptens. Recently, a new colloidal label has been introduced based on elemental carbon. With this carbon label we have prepared a human chorionic gonadotropin-specific dipstick assay with a sensitivity of 10 mIU/ml. In addition, an image- and data-processing procedure for the quantification of the dipstick assay has been developed. The sum of the pixel grey levels of a carbon line was taken as a measure for this quantitative purpose. The measurement range of the assay is almost three orders of magnitude, i.e. 10 mIU/ml to 500 mIU/ml. The deviation from the mean of two dipstick determinations was 1.22% on average. The within-run and between-run precision, expressed as coefficients of variation at 50 mIU/ml were 1.03% and 1.84%, at 150 mIU/ml 2.14% and 3.77% and at 450 mIU/ml 2.55% and 5.28%, respectively. We have correlated this quantitative sol particle immunoassay with a commercial human chorionic gonadotropin specific radioimmunoassay. In an experiment with 25 human urine samples containing the hormone in amounts from 5 to 300 mIU/ml the correlation coefficient was 0.999. The sol particle immunoassay quantified by computer image analysis has been termed Sol particle Image Processed ImmunoAssay (SIPIA).

Publication types

  • Comparative Study

MeSH terms

  • Carbon
  • Chorionic Gonadotropin / urine*
  • Colloids
  • Humans
  • Image Processing, Computer-Assisted* / statistics & numerical data
  • Male
  • Radioimmunoassay
  • Reagent Strips*
  • Regression Analysis
  • Sensitivity and Specificity


  • Chorionic Gonadotropin
  • Colloids
  • Reagent Strips
  • Carbon