title: False-positive results of plasma PCR for cytomegalovirus DNA due to delayed sample preparation.
abstract: Positive results by cytomegalovirus (CMV) PCR of plasma are considered predictive of active CMV infection in kidney allograft recipients. To assess whether contamination with leukocyte-derived CMV DNA can distort the results, aliquots of whole-blood samples from 60 CMV immunoglobulin G-positive patients with leukocyte CMV DNAemia were stored for up to 24 h at room temperature (RT) and at 4 degrees C before plasma preparation. Native and ultrafiltered plasma samples were tested by CMV and beta-globin PCRs. Among 30 latently infected patients (negative for CMV pp65 antigens), low baseline rates (10%) and levels (median number of copies, 10 [per 10 microl]) of CMV plasma DNAemia in native plasma samples increased significantly over time (after 4 h at RT, 37% [P < 0.001]; median number of copies, 45 [P < 0.001]). Similar effects were found during storage at 4 degrees C. Ultrafiltration reduced the levels of CMV plasma DNAemia, but by 6 h of storage the levels were significantly elevated as well. CMV and beta-globin DNA kinetics in plasma were parallel. In contrast, 30 actively infected patients (pp65 positive) had high baseline rates (87% in native samples) and levels (median number of copies, 75) of CMV plasma DNAemia. No significant effects of storage or ultrafiltration and no concordance with beta-globin DNA kinetics were seen. In conclusion, delayed preparation of plasma samples bears a significant risk of false-positive CMV PCR results, probably due to leukocyte lysis. This has important implications in the clinical setting and for PCR standardization.
authors.affiliation: Institut für Medizinische Mikrobiologie und Immunologie, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany. pschaefe@uke.uni-hamburg.de
authors.forename: P
authors.initials: P
authors.lastname: Schäfer
authors.forename: W
authors.initials: W
authors.lastname: Tenschert
authors.forename: M
authors.initials: M
authors.lastname: Schröter
authors.forename: K
authors.initials: K
authors.lastname: Gutensohn
authors.forename: R
authors.initials: R
authors.lastname: Laufs
mesh_terms: D001800:Blood Specimen Collection; D003587:Cytomegalovirus / Q000235:genetics / Q000302:isolation & purification*; D003586:Cytomegalovirus Infections / Q000175:diagnosis* / Q000821:virology; D004279:DNA, Viral / Q000097:blood*; D005189:False Positive Reactions; D005914:Globins / Q000032:analysis; D006801:Humans; D016030:Kidney Transplantation / Q000009:adverse effects; D007963:Leukocytes, Mononuclear / Q000821:virology; D016133:Polymerase Chain Reaction / Q000379:methods*; D013997:Time Factors; D014462:Ultrafiltration
chemical_list: D004279:DNA, Viral; D005914:Globins