Newborn ScreeningQuality Assurance ProgramNewborn ScreeningQuality Assurance Program
Comparison of Less Sensitive HIV Incidence Tests for the Serological Testing Algorithm for Recent HIV
Seroconversion (STARHS)
J. Schiffer, B. Byers, B. Branson, S. Ethridge, K. Delaney, J. Mei
Comparison of Less Sensitive HIV Incidence Tests for the Serological Testing Algorithm for Recent HIV
Seroconversion (STARHS)
J. Schiffer, B. Byers, B. Branson, S. Ethridge, K. Delaney, J. Mei
Centers for Disease Control and PreventionAtlanta, GA 30341
Centers for Disease Control and PreventionAtlanta, GA 30341
Background
• STARHS uses a modified protocol of the bioMerieux Vironostika HIV-1 MicroElisa system (V-LS)- To be replaced in 2005
• We investigated the comparability of the replacement test, Vironostika HIV-1 Plus O (VPlusO-LS)
• Longitudinal specimens from the HIVNET Infected Participant Cohort (IPC) were tested using both kits
Methods
• IPC specimen set • 1009 specimens from 105 recent
seroconverters
• Known dates of last negative and first positive HIV test
• Tested in triplicate on both assays
Methods
• Window Period Calculation– 324 specimens from 59 patients
• 3 or more specimens collected before starting antiretroviral therapy (Mean length of follow up 504 Days)
• Mean window period definition– Number of days between detection of HIV
antibody with a standard EIA and a threshold SOD of 1.0 with the LS-EIA
Results
• V-LS classified 459 samples as incident (SOD<1), and VplusO classified 472 as incident (90.2% concordance).
• Specimen SOD’s diminished after patients started antiretroviral therapy.
V-LS vs. VplusO-LS Sqrt SOD
y = 0.996x + 0.0356
R2 = 0.8482
0
0.5
1
1.5
2
2.5
3
3.5
0 0.5 1 1.5 2 2.5 3
V-LS Sqrt SOD
Vp
lusO
-LS
Sq
rt S
OD
Table 1: Window Period and Confidence Intervals for LS Tests
Vironostika-LS Vironostika Plus O-LS
SODCutoff
WindowPeriod
95%Confidence
Interval
N (Patients, Samples)
WindowPeriod
95%Confidence
Interval
N(Patients, Samples)
0.7 157 140-189 59, 314 142 127-157 59, 324
0.8 179 157-202 59, 314 163 149-184 59, 324
0.9 198 174-224 59, 314 183 167-218 59, 324
1 218 193-250 59, 314 203 185-243 59, 324
1.1 241 214-275 59, 314 225 203-264 59, 324
Two-Year Rule
• SODs tended to plateau or decline after 2 years from last negative specimen.• May result in longer window periods
• New window periods calculated excluding specimens collected after 2 years from last negative test
Window Period (SOD
= 1)
95% Confidence
Interval
N (Patients, Samples)
Vironostika-LS (IPC, 2 year cutoff)
212 187-244 59, 290
Vironostika Plus O-LS (IPC, 2 year cutoff)
196 177-228 59, 294
Vironostika-LS (SFMHS, 2003)
170 145-200 48, 227
Table 2
Window periods and confidence intervals for V-LS and VplusO-LS calculated with the two year cutoff rule applied to the IPC sample set. The V-LS window period previously published using the SFMHS sample set (Kothe et al. 2003) is shown for comparison.
Acknowledgements• Chip Sheppard and Sean Watson of the
California Department of Health Services for providing the HIVNET IPC specimens, without which this work would not have been possible.
• We would also like to thank Debra Kuehl, Silvina Masciotra, Hetal Patel, and Donna Rudolph for their help with organizing and aliquoting the IPC sample set