HIV and ID Observations

Since I first discussed the disruptive effect of introducing Mr. TaqMan to our clinic, many others have weighed in.

One of my favorite reports is a nice paper from the Alabama group, presented first at IDSA, and soon to be published.  It shows not only a higher rate of low-level detectable results, but also the increased costs (substantial) due to repeat testing, resistance genotypes sent (and not yielding anything, of course), and the waste of patient and clinic time.

Today, a new complaint:  the convoluted word salad that follows the results.  To wit, here’s one recent lab report:

HIV-1 PCR:  Detected (H)
HIV-1 PCR QUANT:  170 [yes, 6 prior values were undetectable]
HIV-1 PCR QUANT LOG:  2.23
HIV PCR Interpretation:  SEE BELOW

Comments: The quantitative range of this assay is 48-10,000,000 copies/ml (1.7-7.0 log copies/ml).  In addition to the sample result being expressed as both copies per milliliter (copies/ml) units and as log(copies/ml), this report interprets if the virus was “Detected”, “Not detected” or “Detected but below Quantitative range” as described below in more detail:
a) “Detected” – means that the viral titer in the sample is above the assay’s lower limit of quantitation (48 copies/ml);
b) “Detected – Not Quant” – means that the viral titer in the sample is below the lower limit of quantitation but above the assay’s lower limit of detection ranging from less than 15 to 46 copies ml across all subtypes of HIV-1 group M;
c) “Not Detected” – means that the viral titer in the sample is below the assay’s lower limit of detection. An interpretation of “Not Detected” does not rule out the presence of HIV-1 that is no detectable for reasons such as PCR inhibitors or HIV-1 virus RNA concentrations below the lower level of detection of the assay.
This test is intended for use in conjunction with clinical presentation and other laboratory indices of disease status as an aid in the clinical management of HIV-1 infected patients. The test can be used to assess patient prognosis by monitoring the effect of antiretroviral therapy on changes in plasma HIV-1 RNA levels during the course of treatment.  Limitations:  The COBAS AmpliPrep/COBAS TaqMan HIV-1 Test is not intended for use as a screening test for the presence of HIV-1 in blood or blood products or as a diagnostic test to confirm the initial presence of HIV-1infection. General Disclaimer:  Interpretation of this test may be affected by the presence of rare viral RNA variants. Methodology:  The COBAS AmpliPrep/COBAS TaqMan HIV-1 Test utilizes automated specimen preparation followed by automated reverse transcription, PCR amplification and detection of cleaved dual-labeled detection probes specific to the HIV-1 target RNA. One copy of HIV-1 RNA is equivalent to 1.7 +/- 0.1 International Units (IU) based on the WHO 1st International Standard for HIV-1 RNA for Nucleic Acid-Based Techniques (NAT) (NIBSC 97/656). Test Lab: This assay is approved for In Vitro Diagnostic (IVD) use by the FDA. This test is used for clinical purposes, and it should not be regarded as investigational or for research.

Yikes.

One of my colleagues has responded by going back to sending bDNA.  Yes, that test might be less sensitive, but can anyone tell us yet whether these low-level detectable values have any clinical meaning?