Evaluation of the Abbott Alinity S and the Roche Cobas e801 for - - PowerPoint PPT Presentation

Evaluation of the Abbott Alinity S and the Roche Cobas e801 for Virology screening at the South African National Blood Service

Charl Coleman, Jabu Jaza, Solly Machaba, Marion Vermeulen South African National Blood Service

Introduction

• SANBS test all donations for Human Immunodeficiency Virus

(HIV), Hepatitis C (HCV) and Hepatitis B (HBV)

• Nucleic Acid Testing (NAT) and Viral Serology Testing (anti-HIV,

anti-HCV and HBV Surface Antigen (HBsAg) are performed

• Viral Serology was performed on the Abbott Prism for the past

15 years at SANBS

Introduction

• Aim to evaluate two new viral serology systems

Roche Cobas e801 (Cobas) Abbott Alinity S (Alinity)

• A third system namely the Siemens Atellica was also part of the original evaluation plan, but

the system installation was not successful and in time for evaluation

Background

• Cobas assays HIV Duo (5th gen), HBsAg and anti-HCV
• Alinity assays Alinity HIV Ag/Ab (4th gen), HBsAg and anti-HCV
• The HIV assays for Cobas and Alinity are both able to detect HIV antigen and antibody

compared to the previous Abbott Prism assay used that were antibody only detection

• The detection of antigen is not an added benefit for SANBS, because of NAT testing
• SANBS do perform the p24 antigen test though on all NAT reactive, anti-HIV negative donors in
• rder to provide detail regarding the window period stage and also to compare data to pre-

NAT screening data when p24 antigen testing was performed on all donors

Methods

• Specificity was determined by testing approximately 200-300 first time donor specimens from Johannesburg

and Durban Donation Testing laboratories (December 2017 and May 2018)

• All discordant reactive samples were confirmed using the NAT result (Procleix ULTRIO Elite) or confirmatory

testing for anti-HIV (Biorad Geenius), HBsAg (Roche e411 neutralization) or anti-HCV (Roche e411 HCV and Innogenetics HCV INNO LIA Score)

• Specificity was determined (HIV N=3953, HCV N=3899 and HBsAg N=3953) as per calculation True Negatives

(TN) / (False Positives + TN) x 100

• Sensitivity was evaluated by comparing confirmed positive plasma (NAT Reactive, anti-HIV reactive) and a

panel of HIV NAT yields (p24 positive and p24 negative)

• The Chi-squared test was used to test for statistical significance
• The coefficient of variation (%CV) was calculated from inter (x30) - and intra-run repeats

(10x across 3 runs) of custom quality controls. Instrument failures were recorded

• The total uptime of each instrument was recorded as well time spend on maintenance. The analyzer

maintenance uptime ratio was calculated as the % Total maintenance time/Total uptime

Methods

• The intra assay variation - variation of results within a data set obtained from one run
• The inter assay - variation of results obtained from repeated runs (x3)
• Coefficient of variation (%CV) = Standard deviation of observation/Mean

Donor samples (HIV N=3953, HCV N=3899 and HBsAg N=3953)

Specificity Sensitivity

Plasma 20x HIV NAT Yield, p24 antigen positive Plasma 20x HIV NAT Yield, p24 antigen negative (VL>1000 cp/ML)

Variability

Inter-run comparison 3 x runs of 10 per marker Intra-run comparison 30x HIV, HBsAg and HCV

Instrument reliability (MTBF)

Plasma 15X HIV Confirmed positives (NAT Reactive, anti-HIV reactive) Prism S/CO <20 Plasma 15X HIV Confirmed positives (NAT Reactive, anti-HIV reactive) Prism S/CO >20 Plasma 15X HBsAg Confirmed positive S/CO ratio >20 Plasma 15X HBsAg Confirmed positive S/CO ratio <20 Plasma 13X Anti-HCV Confirmed positive

Results

• Although there were differences in specificities, it was found to be statistically insignificant (HIV

p=0.57, HBsAg p=0.49 and HCV p=0.17)

• The biggest difference in specificity on HCV
• The overall difference in specificity between the systems were 0.15% in favor of Alinity

HIV HBsAg HCV

99.95% 99.95% 99.77% 99.97% 99.90% 99.90%

Specificity of the assays on the Cobas e801 vs the Abbott Alinity S Cobas Alinity

Results

• Sensitivity on donors samples (HIV N=3953, HCV N=3899 and HBsAg N=3953) were

100% for both Cobas and Alinity

• Sensitivity determined by p24 antigen positive confirmed NAT yield samples was

95% (19/20) on both Cobas and Alinity

• The sample not detected by both had a viral load of 37,537 copies per mL with a

p24 antigen positive result S/Co ratio of 1.56

• Sensitivity determined by p24 antigen negative HIV confirmed NAT yields was 4/19

(21%) on Cobas and 5/19 (26%) on Alinity (4/5 positive by both systems and one detected by Alinity only)

Results

• Total uptime on Cobas during evaluation was 432 hours compared to 310 hours for

Alinity

• No failures occurred on Cobas whereas one failure (not leading to downtime)
• ccurred on Alinity therefore MTBF could not be calculated
• Analyser maintenance time ratio was calculated as 8.9% for Cobas compared to

10.4% for Alinity

• The Alinity took approximately 30 – 40 min per day (preparation and instrument

maintenance running time) whereas the Cobas required 23 minutes daily (no preparation, only instrument maintenance running time)

Results

• A %CV of less than 10% is desirable
• Cobas S/CO ratios obtained through repeat sampling are narrower than that obtained from Alinity

Cobas Alinity

3.10% 6.71%

Coefficient of Variation (%CV) achieved in inter- and intra-run comparisons for Cobas and Alinity

Discussion

• The Abbott Alinity S was selected by SANBS mainly due to specificity criteria, which

was the most important aspect of the evaluation

• Specificity has a direct impact on the number of available units for transfusion and

the amount of confirmatory work required

• The largest specificity difference was on anti-HCV. The total difference in specificity

across all markers of 0.15% in favor of Alinity was considered

• With a collection target of 900,000 units per annum, 1350 less donors would be

deferred and the loss of units valued at R2, 521,800 per annum would be avoided

• The sensitivity and reproducibility criteria was met by both Cobas and Alinity. Both

system showed robustness with little downtime occurring

Thank you…