Your Results Are Your Controls: Inclusion of Critical Test Controls

Abstract

Molecular methods, including nucleic acid-based technique such as PCR technique, and antibody-based techniques such as enzyme-linked immunosorbent assay (ELISA), are alternative methods for routine analysis of foodborne pathogens. Inclusion of proper analytical controls is an absolute prerequisite for successful implementation of molecular methods for diagnostic purposes. This chapter describes the selection and inclusion of the analytical control(s), its use, interpretation, applications, and limitations, using PCR and ELISA techniques as examples. It also touches upon the inclusion of controls associated with biosensors and lab-on-a-chip. Negative and positive controls are generally included in most molecular methods and are used to verify that the assay used is able to detect the target and to rule out the risk of cross-contamination during the analysis step. The chapter describes the specific controls needed for PCR and antibody-based methods. Another important type of controls includes process controls, with the purpose of verifying that all steps in the detection process work as intended. These steps can include sample treatment and nucleic acid extraction, together with amplification and detection. There are two types of process controls: positive process control and negative process control. In addition, the positive process control can be combined with an internal amplification control (IAC) by addition of a suitable strain or DNA at the beginning of the analysis chain. Finally, the chapter discusses quantification controls used in real-time PCR and antibody-based methods.