Major Discrepancies of HCV Viral Loads Determined by Real Time Polymerase Chain Reaction Caused by Use of Collection Tubes that Differ Only with the Presence or Absence of Serum Separator.

BACKGROUND: For viral load (VL) analysis of hepatitis C virus (HCV) by Real Time PCR, approved collection tubes were lavender top (LTT) and plasma processing (PPT) tubes, that differ in that PPTs include plasma separator. Using a Real Time PCR method, we investigated how the results correlated for the two tube types.

METHODS: The plasma fractions of blood samples from each of 202 patients were collected in LTT and PPT tubes at the same time and were assayed for HCV VL by the Abbott m2000 Real Time PCR System; the results were analyzed statistically.

RESULTS: VLs for 103 samples for both tubes were negative. Positive results were obtained for another 79 tube pairs, including six with VLs for LTTs but values below linearity for the corresponding PPTs. For the 73 samples for which quantitative results were obtained for both tube types, VLs were statistically higher in LTTs (means 1,817,821.8 in LTTs and 1,083,669.1 in PPTs, p =0.006, alpha=0.05) using the paired t-test and confirmed by the Chi Square and McNemars tests.

CONCLUSIONS: VLs in LTTs are significantly higher and more sensitive than in PPTs, suggesting the necessity of standardization of collection tubes for HCV VLs.