title: Validation of dilution of plasma samples with phosphate buffered saline to eliminate the problem of small volumes associated with children infected with HIV-1 for viral load testing using Cobas AmpliPrep/COBAS TaqMan HIV-1 test, version 2.0 (CAP CTM HIV v2.0).
abstract: The sample requirement of 1 mL for the Roche COBAS AmpliPrep/COBAS TaqMan HIV-1 test, version 2.0 (CAP CTM HIV v2.0) limits its utility in measuring plasma HIV-1 RNA levels for small volume samples from children infected with HIV-1. Viral load monitoring is the standard of care for HIV-1-infected patients on antiretroviral therapy in Botswana. The study aimed to validate the dilution of small volume samples with phosphate buffered saline (1× PBS) when quantifying HIV-1 RNA in patient plasma. HIV RNA concentrations were determined in undiluted and diluted pairs of samples comprising panels of quality assessment standards (n=52) as well as patient samples (n=325). There was strong correlation (R(2)) of 0.98 and 0.95 within the dynamic range of the CAP CTM HIV v2.0 test between undiluted and diluted samples from quality assessment standards and patients, respectively. The difference between viral load measurements of diluted and undiluted pairs of quality assessment standards and patient samples using the Altman-Bland test showed that the 95% limits of agreement were between -0.40 Log 10 and 0.49 Log 10. This difference was within the 0.5 Log 10 which is generally considered as normal assay variation of plasma RNA levels. Dilution of samples with 1× PBS produced comparable viral load measurements to undiluted samples.
authors.affiliation: Botswana Harvard HIV Reference Laboratory, Princess Marina Hospital, 1836 North Ring Road, Gaborone, Botswana; National Health Laboratory, 5353 Church Road, Extension 10, Gaborone, Botswana. Electronic address: mmine@bhp.org.bw.
authors.forename: Madisa
authors.initials: M
authors.lastname: Mine
authors.forename: Tapologo
authors.initials: T
authors.lastname: Nkoane
authors.forename: Gaseene
authors.initials: G
authors.lastname: Sebetso
authors.forename: Bright
authors.initials: B
authors.lastname: Sakyi
authors.forename: Kgomotso
authors.initials: K
authors.lastname: Makhaola
authors.forename: Tendani
authors.initials: T
authors.lastname: Gaolathe
mesh_terms: D001902:Botswana; D002021:Buffers; D002648:Child; D015658:HIV Infections / Q000175:diagnosis* / Q000821:virology*; D015497:HIV-1 / Q000302:isolation & purification*; D006801:Humans; D025202:Molecular Diagnostic Techniques / Q000379:methods*; D010710:Phosphates; D010949:Plasma / Q000821:virology*; D012965:Sodium Chloride; D013048:Specimen Handling / Q000379:methods*; D019562:Viral Load / Q000379:methods*
chemical_list: D002021:Buffers; D010710:Phosphates; D012965:Sodium Chloride
keywords: COBAS TaqMan HIV-1 test; Dilution; HIV-1 RNA; Viral load