Comparison of real-time PCR quantitative analysis of the cytomegalovirus DNA level using LightCycler 2.0 and LightCycler 480 instruments.

UNLABELLED: Cytomegalovirus infection is a frequent complication after transplantation. It is commonly believed that the level of CMV viraemia, usually measured with real-time PCR, is directly correlated with the risk of developing a serious cytomegaloviral disease.

OBJECTIVES

The aim was the comparison of results obtained with a commercial test for the quantitative diagnostics of CMV infections, using LightCycler 2.0 and LightCycler 480 real-time PCR systems.

STUDY DESIGNS: Study comprised 97 samples of nucleic acids isolated from serum, in which the CMV DNA was detected during routine tests. Measurement in both analysers was performed simultaneously for paired serum samples. Comparison and of the results obtained with two types of thermocyclers included regression analysis, Spearman correlation, Friedman test and Bland-Altman analysis (p<0.05).

RESULTS

CMV DNA was detected in all samples with use of both thermocyclers. Correlation coefficient of results obtained with both analysers was 0.94. According to Friedman and Bland-Altman tests' results, there were significant differences in measurements between instruments (p<0.001 and p=0.017, respectively). Difference of median values was 0.137 log(10)CMV viral load/ml, and difference of mean values was 0.215 log(10)CMV viral load/ml. Clear threshold of fluorescence crossing point of 1.4-1.8 cycles in advantage of LightCycler 480 was an apparent difference between both analysers.

CONCLUSIONS

There was good overall correlation between both analysers, as detected shift in both median and mean values was close to intra-assay variability declared by its producer. Observed differences were probably due to different fluorescence excitation and detection systems used in both instruments.