Labtech

Quality Control in Diagnostic Laboratories

Quality control product is a patient-like material ideally made from human serum, urine or spinal fluid

Dhiren Wagle

Achieving quality control in a medical laboratory requires the use of many tools. These include procedure manuals, maintenance schedules, calibrations, a quality assurance programme, training and quality control (QC).

QC in the medical laboratory is a statistical process used to monitor and evaluate the analytical process, which produces the patient results. The statistical process requires regular testing of QC products along with the patient samples, and comparison of QC results to specific statistical limits.

When a diagnostic test is performed in a laboratory, the result may be a patient result or it may be a QC result. The result may be quantitative, qualitative or semi-quantitative.

QC results are used to validate patient results. Once validated, the patient results can then be used for diagnosis, prognosis or treatment planning. The reliability, accuracy and precision of the results can be determined by regular use of QC material and the related statistical process control.

Quality Control Product

QC product is a patient like material ideally made from human serum, urine or spinal fluid. A control product can be liquid or freeze dried (lyophilised). Control products must be tested in the same manner as the patient sample. It is usually a multi-analyte with a range for each analyte.

A control is a 'patient-like' sample composed of one or many constituents whose concentrations are known. A range of acceptable values with upper and lower limits represents the constituent or analyte concentrations. Controls are used to monitor the precision and accuracy of the diagnostic testing system.

When the observed control values fall within the acceptable range, the laboratorian can confirm the test system is working properly and the patient results can be reported with confidence.

It is extremely important that the controls are third party controls. Unbiased assessment or third party controls are controls, which are not optimised for a specific test, kit, reagent system or instrument. Many instrument or kit manufacturers supply controls that are designed or 'optimised' to that specific instrument or kit. Third party control acts as a patient sample to give an unbiased assessment of the test system.

Certification & Accreditation

ISO certification is the certification of an organisation's quality management systems and demonstrates that the lab has established quality management system. However, it does not address the compliance to technical competence of the laboratory.

For a medical laboratory, however, in addition to certification, accreditation is of greater significance. Accreditation involves the assessment of a laboratory by an external independent body (a laboratory accreditation body) to evaluate the laboratory's technical competence in performing tests, calibrations, sample taking and handling, reporting as appropriate. It evaluates the implementation of laboratory's quality system based on criteria set down in ISO 15189. Accreditation also requires satisfactory performance in an on going proficiency programme.

National Accreditation Board for Testing and Calibration Laboratories (NABL) has been established with the objective to provide Government, industry associations and industry in general with a scheme for third party assessment of the quality and technical competence of testing and calibration laboratories. The Government of India has authorised NABL as the sole accreditation body for testing and calibration laboratories. NABL has established its accreditation system in accordance with ISO/IEC Guide 58, which is followed internationally. In accordance with ISO/IEC Guide 58, NABL is required to conduct inter-laboratory proficiency testing. Besides, as per provisions for ISO/IEC Guide 25 (1990) the accredited laboratories are required to take part in inter-laboratory proficiency testing.

One of the objectives of accreditation bodies is to encourage proficiency tests/inter-laboratory comparisons in order to ensure accuracy, reliability and reproducibility of test results. Accreditation bodies also encourage the use of third party controls.

Medical Labs & Quality Standards

Use of third party controls and participation in external quality assurance programmes not only provides a laboratory added confidence in the reporting of the results but also helps a laboratory to demonstrate compliance to the highest quality systems.

This further enables a laboratory easy compliance to accreditation/certification requirements. Such certifications provide a laboratory a better standing, and does away with botheration of facing medico legal issues.

E-mail: dhiren_wagle@bio-rad.com
The writer is Country Manager Bio-Rad India NCR Delhi