QUALITY CONTROL

Quality Control relies heavily on quantitative statistical methods that focus on the final product, as defined by standards set by the producer.

TYPES OF QUALITY CONTROL

• Internal Quality Control - Monitors the day-to-day performance of lab test, namely precision.
• External Quality Control - Monitors primarily the accuracy of lab tests

LAB PRACTICES ON QUALITY CONTROL

Division of Lab Practice in QC

• Preventive Procedures - pre-analytic activities that are intended to establish a system which leans towards providing accuracy.These preventive measures include performance checks and calibration of equipment, examination of user-prepared and commercially-prepared media and orientation and training of lab staff
• Assessment Practices - analytic activities that are done during the test to determine whether the established systems are performing correctly. The use of standards and controls, as well as control chart maintenance is included in the assessment practices.
• Corrective Practices - post-analytic activities to determine error and possible sources of error to be able to correct the established system. Activities in the corrective practices include troubleshooting of equipment used, recalibration of instruments, retraining of staff, etc.

Control of Tests

• Precision – It can be assessed intra-laboratory and inter-laboratory. It is determined by how well a procedure reproduces a value.
• Accuracy – commonly known as the “gold standard” if refers to the closeness of a result to the actual value of an analyte when performing a test.
• Sensitivity – is the percentage of individuals with particular disease for which the test is used in whom positive results are found.
• Specificity – is the percentage of individuals who do not have the particular disease and whom negative results are found.

Control of Specimens

These instructions should be available to the hospital staff for use when specimens are collected. The written collection instructions should include:

• Test purpose and limitation
• Patient selection criteria
• Timing of specimen collection
• Optimal specimen collection sites
• Approved specimen collection methods
• Specimen transport medium, time and temperature
• Availability of test
• Hours test performed
• Result reporting procedures

Control of Reagents and Supplies

• Labs should purchase reagents and supplies from reliable sources
• Containers of reagents should be labeled as to contents, concentration, date opened, expiration date, source, lot number, and storage requirements
• All supplies and reagents should be stored according to manufacturer’s recommendations
• Tested with positive and negative controls before use
• No incidence of lack of supplies for the lab tests offered
• First in, first out must always be followed
• Outdated supplies and reagents that failed QC should be discarded immediately

Control of Staff

Appropriately trained and experienced personnel are essential for the performance of quality laboratory testing. All employees should know what they are supposed to do, and every laboratory should have written job descriptions to provide them. Standards of performance should be developed so that the employee knows how he will be judged when rated on job performance.

Control of Equipment

Equipment and instrument logs should contain the following information:

• Equipment or instrument name; serial number and date 
• Procedure and periodicity for routine function checks
• Acceptable performance ranges
• Instrument function failures, including specific details of steps taken for corrective action
• Date and time of service request and response
• Date of routine preventive maintenance which should follow manufacturer’s recommendations