The HESI studies found significant variation among results of microarray experiments that were caused by differences in procedures among participating laboratories, including different operating procedures for isolating and labeling mRNA samples, nonstandard settings on hardware and software, and differences in gene coverage and annotation across different technology platforms.
We included centre as random effect as the BP measurements generally were higher in the Copenhagen centre than in Aarhus centre, which might be explained by differences in procedures etc. between the two centers.
There is no evidence in literature that the outcome differs for these two procedures, 14, 20 except for a tendency toward an improved long-term survival in the extended transthoracic group in the study of Hulscher et al. 21 So the clinical outcome in our population is likely uninfluenced by differences in surgical procedure.
A final factor that complicates meaningful combinatorial analyses of transcriptional regulation is that integration of data from different studies and laboratories may be hampered by differences in experimental procedures for microarray experiments (including the use of different microarray platforms, mRNA extraction, normalization and summarization algorithms [ 3, 4]).
To evaluate the potential effects on sample properties caused by differences in sampling procedures, we assessed the consistency between lake water sampled by the drone and that sampled by hand at site U1 (Fig. 1), where regular samplings had previously been carried out.
First, this might be explained by differences in staining procedures.
These findings may be explained by differences in screening procedures prior to transplantation and by differences in study populations.
Differences in our results from previous findings may be explained by differences in study procedures and samples (64).
Whilst the reported values for Pb are higher compared with our results (21 - 26.7 mg kg-1), this could be at least partially explained by differences in digestion procedures; recovery for Pb in the Abraham's study was 264% compared to 101% recovery in the present study.
This is caused by differences in the initialisation procedure of the two algorithms.
