Quantification of the islet product: Presentation of a standardized current good manufacturing practices compliant system with minimal variability

Andrew S. Friberg, Heide Brandhorst, Peter Buchwald, Masafumi Goto, Camillo Ricordi, Daniel Brandhorst, Olle Korsgren

Research output: Contribution to journalArticlepeer-review

33 Citations (Scopus)


Background. Accurate islet quantification has proven difficult to standardize in a good manufacturing practices (GMP) approved manner. Methods. The influence of assessment variables from both manual and computer-assisted digital image analysis (DIA) methods were compared using calibrated, standardized microspheres or islets alone. Additionally, a mixture of microspheres and exocrine tissue was used to evaluate the variability of both the current, internationally recognized, manual method and a novel GMP-friendly purity- and volume-based method (PV) evaluated by DIA in a semiclosed, culture bag system. Results. Computer-assisted DIA recorded known microsphere size distribution and quantities accurately. By using DIA to evaluate islets, the interindividual manually evaluated percent coefficients of variation (CV%; n=14) were reduced by almost half for both islet equivalents (IEs; 31% vs. 17%, P=0.002) and purity (20% vs. 13%, P=0.033). The microsphere pool mixed with exocrine tissue did not differ from expected IE with either method. However, manual IE resulted in a total CV% of 44.3% and a range spanning 258 k IE, whereas PV resulted in CV% of 10.7% and range of 60 k IE. Purity CV% for each method were similar approximating 10.5% and differed from expected by +7% for the manual method and +3% for PV. CONCLUSION.: The variability of standard counting methods for islet samples and clinical quantities of microspheres mixed with exocrine tissue were reduced with DIA. They were reduced even further by use of a semiclosed bag system compared with standard manual counting, thereby facilitating the standardization of islet evaluation according to GMP standards.

Original languageEnglish
Pages (from-to)677-683
Number of pages7
Issue number6
Publication statusPublished - 2011 Mar 27


  • Digital imaging analysis
  • GMP
  • Islet evaluation
  • Purity
  • Volume


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