We have a 46 female who have a hCG bteween 12 and 15 UI/L since at least one year. The results are similar after dilution and/or centrifugation at high speed. We report as negative value < 5 and positive > 25. Also we had the same values using a different method. Any ideas why the values are consistently in gray zone? Is interference still a possibility? Thanks Ihssan Dr. Ihssan Bouhtiauy, PhD, FCACB, FACB, MBA Chef clinique du département de Biochimie Réseau de santé Vitalité 275 Blv. Hebert Edmundston NB, E3V 4E4 Canada Courriel: [log in to unmask]<mailto:[log in to unmask]> Tél. (506) 739-2536 ------ACB discussion List Information-------- This is an open discussion list for the academic and clinical community working in clinical biochemistry. Please note, archived messages are public and can be viewed via the internet. Views expressed are those of the individual and they are responsible for all message content. ACB Web Site http://www.acb.org.uk Green Laboratories Work http://www.laboratorymedicine.nhs.uk List Archives http://www.jiscmail.ac.uk/lists/ACB-CLIN-CHEM-GEN.html List Instructions (How to leave etc.) http://www.jiscmail.ac.uk/