Importance of Controls and Calibrators in a clinical analysis laboratory

 

Clinical analysis laboratories are a fundamental part of a health unit, as they directly contribute to the medical team to deliver reliable results for prevention, diagnosis, treatment and management of patients' diseases. The participation of a laboratory in the diagnosis is a process initiated from the pre-analytical phase. This involves preparation of the patient, collection and transport of the material to the laboratory unit; analytical phase, which begins with the processing of collected samples, according to the reliable results of its internal quality control (CIQ), verification of reagents and instruments, and finally the post-analytical phase, which consists of releasing the final report.

Quality Control program

The results of the CIQ (Internal Quality Control), expressed in biochemistry equipment, for example, need to be evaluated daily, to analyze the performance of the analytical system. However, in order not to have an examination result with an unacceptable error, the performance of the analytical system must be measured, evaluated and corrected. In this way, we use calibrators and quality control, which are materials that have the objective of gauging, monitoring and correction. In addition to the CIQ, it is recommended that laboratory units participate in some external Quality Control program, so that it is possible to evaluate their performance in relation to other laboratories.

Ensuring accurate results

The accreditation of clinical laboratories by CAP and NABL (ISO 15189) validates their ability to perform high quality clinical testing and clinical interpretation to international quality standards in every facility that they operate. The CAP laboratory accreditation program is an internationally recognized program that helps laboratories achieve the highest standards of excellence to positively impact patient healthcare. At the same time, patient safety and care, as well as laboratory service quality, are of top priority. The accreditation by NABL, the only government-authorized laboratory accreditation body in India, works in accordance with ISO 15189:2012 standards.

Role of calibrators

The calibrator, also called a standard, is used to transfer the accuracy to the analytical system, that is, to adjust the measurement parameters that are closest to the real value. The difference between standard and calibrator is related to their composition. The standard is usually an aqueous solution (non-protein matrix), specific for only one parameter and the calibrator is constituted by a protein matrix and can be used to calibrate one or more parameters. 

Types of calibrators

Calibrators are classified into liquids and lyophilized. Liquids are ready to use and lyophilizates (powder) must be reconstituted with purified/distilled water for use. The calibrator or standard has a known concentration of a particular analyte and this amount is informed to the equipment so that it can use it as a reference during calibration. 

Figure 1: Erba XL Multical is a lyophilized calibrator based on human serum, biological analytes and 0.095% w/v sodium azide, multi-parameter, with concentrations suitable for use in XL family automatic analyzers.

The role of controls

Controls are used to monitor the stability of the analytical system, evaluating the accuracy, precision and indicating the need for possible calibrations, reagent changes or even corrective maintenance. Analytical systems need to be monitored by normal and pathological level controls and evaluated daily through the results presented in the CIQ (Internal Quality Control). 

Figure 2: Erba Path Control (Pathological)

Figure 2: Erba Path (Pathological), this is a control serum designed to monitor the accuracy and precision of Biochemistry assays used in the pathological range.

It is recommended that laboratories follow the guidelines recommended by the manufacturer for the preparation and storage of controls, calibrators and standards, in order to minimize possible errors that may interfere with the performance of the analytical system.

Author: 

Juliana Oliveira

Master in Pathology

Field Scientific Advisor-Erba Mannheim

 

Bibliography

• Guimarães, AC, Wolfart, M., Brisolara, ML, & Dani, C. 2011. The clinical laboratory and pre-analytical errors. Journal of Hospital das Clínicas de Porto Alegre, 31(1), 66-72
• Pasquini, NC 2018. Implementation of a quality system (PALC) in a clinical laboratory: a case study. Technological Journal of Fatec Americana, 6(1), 82-94.
• Santos, CSS, Barbosa, TCS, Neto, JARF, Melo, CA, Aarão, TLS, & Silveira, MA 2020. Quality control in the Clinical Analysis Laboratory in the Analytical Phase: The Safety of Results. Brazilian Journal of health Review, 3(4), 8512-8523.
• Silva, AP, & Steckert, C. 2019. Applicability of quality tools in the control of clinical laboratory failures. Revista Inova Saúde, 9(1), 115-128. Brazilian Society of Clinical Pathology/Laboratory Medicine [SBPC/ML]. 2021.
• PALC Standard – Clinical Laboratory Accreditation Program. Ed. 2021. Available at http://www.sbpc.org.br/programas-da-qualidade/documentos-do-palc/ .

Source: ERBA PATH – Erba Mannheim Brazil (erbabrasil.com.br)