QUALITY ASSURANCE IN THE CLINICAL CHEMISTRY LABORATORY

Introduction There are many steps in the process between the clinician requesting a clinical biochemistry test and receiving a result. Each of these steps must be subject to quality assurance techniques. Clinical chemistry laboratories now have mature, integrated systems of internal quality control, external quality assessment and quality assurance to ensure that the results issued do aid in the provision of optimum patient care. The recent initiation of a professionally led laboratory accreditation scheme will stimulate further improvements in quality.

Introduction Enthusiastic adoption of the techniques of quality management science, in the form of total quality management systems, will focus future attention on laboratories providing services to the standards dictated by consumers. Translation of these standards into objective operational specifications will then allow laboratories to adopt appropriate comprehensive quality assurance techniques which will guarantee the quality demanded

Quality Assurance of Specimens Serum or plasma collected by venipuncture or capillary puncture is the sample of choice for the majority of chemical methods specimen collected without an anticoagulant, producing serum other methods require that a preservative or anticoagulant be used to Other tests on other fluids are also ordered chemical analysis of urine a limited number of tests are being applied to cerebrospinal fluid and other body fluids for example, glucose and protein tests Regardless of the specimen, it should be properly collected, preserved, and transported to the laboratory

Quality Assurance of Specimens Specimens arriving at the laboratory should be labelled so as to provide clear and unambiguous identification. The identification on the specimen must match that on the request form in all respects. This verification may be done visually on receipt of the specimen in the laboratory but is best done by use of some form of bar-coding. Indeed, an approach to the ideal is for the individual who performs specimen collection, in the ward, to scan the bar-coded identification of the patient prepared by the hospital computer or patient administration systems into the laboratory information system and to nominate the tests required.

Quality Assurance of Specimen Collection & Transportation Sodium fluoride For samples which is necessary to completely stop glycolysis Urine samples (24 h) Preservation with boric acid or hydrochloric acid to prevent loss of various metabolites Transportation of samples to Lab. should be as soon as possible Some samples should be transported on ice blood gases (O2 levels decrease while CO2 levels increase) Some plasma constituents are photosensitive Bilirubin measurement Excessive vibration or rough handling Hemolysis

Quality Assurance of Specimen Separation of Serum or Plasma Once sample is received, it should immediately centrifuged to separate serum or plasma otherwise many changes can occur: RBCs loose their integrity and intracellular components start to leak Glucose and O2 concentration decrease CO2, lactic acid increase while pH becomes more acidic

Quality Assurance of Specimen The Effects of Hemolysis Causes release of RBCs components which will increase the plasma concentrations of: Plasma Hb Which will interfere with bilirubin determinations with any measurements made at 540 nm Potassium Alanine aminotransferase Inorganic phosphorus Copper Lactate dehydrogenase Aspartate transaminase Magnesium Creatinine Kinase Acid phosphatase

Change in concentration Quality Assurance of Specimen Changes due to storage of whole blood at RT Constituent Change in concentration Ammonia Marked increase Bilirubin Mild to marked decrease Total CO2 Carbonic acid Lactic acid Magnesium Mild increase O2 Marked decrease Glucose Decreases Plasma enzymes Mild to marked decrease in activity Protein, sodium, chloride, Creatinine, Calcium Unchanged

Sources of Error in Clinical Chemistry 1. Specimen mix-up A Specimen drawn from wrong patient Specimen labeled with the wrong name or accession numbers Serum transferred into mislabeled tubes Improper cup placed into a tray position and the results reported on the wrong patient 2. Allowing evaporation of a sample while it sits on the analyzer waiting to be analyzed This will concentrate the sample, resulting in higher values 3. Dilution and calculation errors Incorrect dilution of sample Failure to correct for dilution

Sources of Error in Clinical Chemistry 4. Sampling errors Partially clotted specimen Short sampling Air bubble in the bottom of the cup Fibrin clot in the sample probes 5. Transcription errors 6. Instrument losing calibration due to: dirty reaction cuvettes, or worn pump tubing; 7. Instrument is not recalibrated when new reagents are placed on the instrument This can result in a shift in the calibration

Quality Assurance of Basic Laboratory Equipment Many items of basic laboratory equipment are employed in the laboratory and it is important that these are subjected to routine quality assurance The temperature control of major equipment should be monitored using thermometers or electronic devices. The performance of spectrometers should be checked for wavelength calibration using colored solutions or didymium or holmium oxide niters; absorbance must also be monitored regularly using colored solutions https://www.youtube.com/watch?v=W9uzIfkJxh4

Quality Control Internal quality control External quality control

Accreditation of Laboratories The accreditation system is simple. A laboratory approaches Clinical Pathology Accreditation (CPA- UK) and receives an application form and handbook. The handbook acts as a guide to the interpretation of the standards for both inspectors and applicant. The applicant performs in-house assessment against the standards and fills in the form to show compliance with, or exemption from, each of them. On receiving the completed forms, an inspection is arranged by the project office at a convenient time for both inspectors and applicant.

Accreditation of Laboratories There are two inspectors for each laboratory, a consultant grade scientist or pathologist and a senior Medical Laboratory Scientific Officer. Inspectors are trained and appointed by CPA (UK) through its advisory committees. If problems are identified by the inspectors, accreditation is not granted until the difficulties are resolved to the satisfaction of CPA (UK). Accreditation is not withheld on the basis of a single inspection, however

Accreditation of Laboratories The standards required are comprehensive and the 44 requirements cover: organization and administration of the laboratory, staffing, facilities and equipment, policies and protocols, staff education, and evaluation of the service. Many of the standards are concerned with the need for quality assurance methods covering all aspects of laboratory performance.

Total Quality Management A recent trend has been to imitate industry and adopt the beliefs of quality management science to establish total quality management (TQM). The focus of TQM is continuous improvement of quality. The first step is to define the needs of the 'customers' of the laboratory which includes: Clinicians, patients, nurses, administrators, other departments, accreditation inspectors and others.

Total Quality Management The needs of these customers define the quality goals that the laboratory should achieve. Then the laboratory institutes quality planning to guide the implementation and ongoing monitoring provided by quality control and quality assurance. When the quality is unsatisfactory, quality improvement should take place which may impinge upon quality plans.