Evaluation of sample pooling using the SAMBA II SARS-CoV-2 test.

Area of Science:

• Infectious disease diagnostics
• Molecular biology
• Public health

Background:

• Screening asymptomatic or pre-symptomatic individuals for SARS-CoV-2 is crucial for pandemic control.
• Pool testing strategies are being explored to enhance testing capabilities and reduce costs.
• Assay performance must be maintained when implementing pooled testing.

Purpose of the Study:

• To evaluate the performance of the SAMBA II assay for pooled SARS-CoV-2 testing.
• To assess the sensitivity and specificity of pooling four samples (one positive, three negative).

Main Methods:

• Combined nose and throat swabs were tested individually and in pools of four using the SAMBA II assay.
• The evaluation was conducted by the manufacturer and an independent NHS site.
• Cycle threshold (Ct) values of positive samples were determined by quantitative reverse transcription PCR (qRT-PCR).

Main Results:

• Pooling 4 samples demonstrated 97.6% sensitivity, correctly identifying 41 out of 42 single-positive pools.
• One false-negative pool occurred with a very low viral load sample, which was borderline positive by reference methods.
• 100% specificity was achieved, with all 78 pools of negative swabs testing negative.

Conclusions:

• The SAMBA II assay demonstrates high sensitivity and specificity when testing pools of four patient samples.
• Implementing pooled testing with SAMBA II can significantly increase throughput and reduce cost per test.
• This strategy is particularly effective for widespread SARS-CoV-2 screening when COVID-19 prevalence is low.