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Table 1 Performance of the cytomegalovirus PCR assay for quantitation of cytomegalovirus DNA load in tracheal aspirates

From: Need to evaluate the performance of real-time PCR assays for the quantitation of cytomegalovirus DNA load in lower respiratory tract specimens

Group (number of specimens)a Range of CMV DNA loads (copies/ml)b % Coefficient of variation (95 % confidence interval)
   Intra-assay Inter-assay
A (10) 150 to 851 14.0 (9.8 to 18.7) 15.4 (12.1 to 18.8)
B (10) 1,234 to 8,781 10.6 (7.8 to 14.0) 16.2 (11.2 to 21.5)
C (10) 11,013 to 56,000 11.7 (4.9 to 18.5) 12.8 (7.3 to 18.3)
A + B + C (30) 150 to 56,000 14.0 (9.8 to 18.1) 15.4 (12.1 to 18.8)
  1. CMV PCR assay, COBAS® AmpliPrep/COBAS® TaqMan Cytomegalovirus PCR Assay (Roche Diagnostics, Mannheim, Germany). aTracheal aspirates were obtained from 20 patients with septic shock of abdominal origin admitted to the ICU. On the basis of their cytomegalovirus (CMV) DNA content, the specimens were grouped into three categories: A, between 150 and 1,000 copies/ml; B, between 1,000 and 10,000 copies/ml; and C, >10,000 copies/ml. The specimens were divided into the above referred groups based on two criteria: the precision of the Roche PCR assay for plasma specimens was shown to vary depending upon the CMV DNA content – in this sense, the coefficient of variation was maximum for specimens containing <1,000 copies/ml, minimum for those containing >10,000 copies/ml, and intermediate for specimens containing CMV DNA loads between 1,000 and 10,000 copies/ml [5]; and the majority of tracheal aspirates from critically ill patients displaying an episode of active CMV infection contain CMV DNA loads <1,000 copies/ml, so the knowledge of the performance of the PCR assay with specimens containing CMV DNA loads within this range (150 to 1,000 copies/ml) is of particular clinical interest. Only occasionally, tracheal aspirates contain >10,000 copies/ml. bAs determined by the CMV PCR assay. This PCR assay targets the CMV UL54 gene (DNA polymerase) and displays a limit of detection of 100 copies/ml (91 IU/ml), a limit of quantification of 150 copies/ml (164 IU/ml), and a linear quantification range from 150 to 10,000,000 (2.18 to 7.0 log10) copies/ml for plasma specimens.