Method Verification of Cepheid Xpert Xpress Flu Assay by Polymerase Chain Reaction (PCR)

Graduation Date


Document Type

Master's Thesis

Degree Name

Master of Science

Department or Program

Clinical Laboratory Sciences

Department or Program Chair

Mary Sevigny, PhD

First Reader

Rachel F. Inuremerable, CLS

Second Reader

Maria C. DeSousa, JD, MPA, CLS


Method Verification of Cepheid Xpert Xpress Flu Assay by Polymerase Chain Reaction (PCR) was performed in accordance with California Pacific Medical Center (CPMC) laboratory protocol and Clinical and Laboratory Standards Institute (CLSI) Evaluation Protocol, EP15-A2. Method verification plan involves planning phase to define the requirement of the test, generate validation data and implement the test. For precision testing, positive and negative quality controls (QC) were run in 20 consecutive days. Precision is determined as 100% as all 20 QC results passed and agreed with expected values. Nasopharyngeal swabs in viral transport media (VTM) were the only patient specimens approved for validation. Method comparison of current Flu PCR, Combo Flu/RSV testing and Sofia rapid flu, an enzyme linked immunosorbent assay (EIA) testing includes 9 positive results and 11 negative reflexed results. Current Polymerase Chain Reaction (PCR) flu/RSV testing results proved and verified 100% in agreement with the Xpert Xpress Flu results. Turnaround times (TAT) differ in each test platforms. Sofia rapid flu TAT is 15 minutes while PCR combo flu/RSV assay is 60 minutes. The new Cepheid Xpert Xpress flu is only 30 minutes. Minimum sample size of 20 patient specimens recommended but not ideal, will affect computation of clinical performance in comparative study of PCR and EIA methods. In addition, implementation of the new Cepheid Xpert Xpress flu Assay test requires incorporating it into the workflow of the laboratory and the completion of several documents. A complete procedure must be written and signed by the Laboratory Director, and it should include such elements as indications, intended use, principle of the test, specimen handling and storage, reagents, controls, equipment, step-by-step procedure, guide for analytic interpretation, and references. The objective of this project is to compare the analytical performance of the new Cepheid Xpert Xpress Flu Assay by PCR with current CPMC laboratory Flu testing

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