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