[Calibration of false positive result in detection of BCR/ABL using fluorescence in situ hybridization]

To explore the effect of false positive signals during detection of BCR/ABL fusion gene by fluorescence in situ hybridization (FISH), and develop a method for calibration.

Normal specimens were mixed with BCR/ABL positive specimens in which presented signal pattern of 1-red-2-green-1-fusion (1R2G1F) using dual color dual fusion (DCDF) probes and 1-red-1-green-1-fusion (1R1G1F) using extra signal (ES) probes in different proportions. Mixed samples were detected using DCDF and ES probes. Results of DCDF probes, ES probe before calibration, ES probes after calibration and theoretical results were compared by binomial distribution in different proportions.

The rate of false positive signals has risen with increase of negative rate. A significant difference was found between theoretical proportion and results without calibration in negative level, 5%, 10% and 25% positive level (P<0.05). There was no significant difference between theoretical proportion and results without calibration in 50% and 90% positive level (P>0.05). Also there was no significant difference between theoretical proportion and calibrated results (P>0.05).

Calibration of FISH result can delimitate the effect of false positives, and can provide more reliable results in cases with low level positive rates.