The Lo-Alter team's findings have come under scrutiny as possibly due to contaminants associated with common laboratory reagents. Phylogenetic analysis conducted by Katzourakis et al. and other groups suggest the sequences identified by Lo et al. in samples from CFS patients collected 15 years apart were not consistent with evolutionary change and were likely due to contamination of the samples with 22RV1, a prostate cancer cell line. The work by Katzourakis is cited in the retraction notice by the authors, although they also state, "there has been no evidence of contamination using sensitive mouse mitochondrial DNA or IAP assays or in testing coded samples…"