Module 11
Compliance with established quality assurance requirements
Purpose / To provide you with an understanding of the quality assurance system and its importance in the TB laboratory.Prerequisite modules / Modules 2 - 10
Module time / 1 hour 20 minutes, + 1 hour for exercises
Learning objectives / At the end of this module you will be able to:
‒ explain the three main components of the QA system and their importance;
‒ adhere to QC and EQA procedures.
Content outline / • Quality assurance (QA) in mycobacteriology
• Quality control (QC)
• External quality assessment (EQA)
• Quality improvement (QI)
Exercise / Evaluate indicators
INTRODUCTION
This module explains the importance of the quality assurance (QA) system in the mycobacteriology laboratory and the main requirements. Some more specific requirements for a particular procedure or item of equipment have been already explained in the relevant modules.
The QA system is the basis for a guaranteed result. If this system is not followed, patients may get the wrong results, with important consequences for their health – such as not receiving adequate treatment.
QUALITY ASSURANCE IN THE MICOBACTERIOLOGY LABORATORY
The QA system is designed to continuously improve the reliability, efficiency and use of laboratory services in order to achieve the required technical quality in laboratory diagnosis. The three main components of this system are:
• Internal quality assurance (IQA) or Quality control (QC): includes all means by which the TB laboratory controls its operations, including instrument checks and checking new lots of staining solutions, reagents and media.
• External quality assessment (EQA): a process that allows participating laboratories to assess their capabilities by comparing their results with those in other laboratories in the network (intermediate and central laboratory) through panel testing. EQA also includes on-site evaluation of the laboratory to review quality of performance. EQA is an expansion of the proficiency testing described by IUATLD.
• Quality improvement (QI): a process by which the components of TB diagnostic services are analysed with the aim of finding ways to permanently remove obstacles to success. Data collection, data analysis and creative problem-solving are the key components of this process. IQC involves continued monitoring and identification of defects, followed by remedial action –including retraining when needed – to prevent the recurrence of problems. QI often relies on effective on-site evaluation visits.
The QA process should be continuous and monitored, and should involve all levels of the laboratory network –peripheral, intermediate and central laboratories.
QUALITY CONTROL
Quality control is a process of effective, systematic monitoring of all laboratory activities: it guarantees that laboratory data are accurate, reliable, reproducible and comparable. QC establishes limits of acceptable standards of test performance; it is the responsibility of all laboratory technicians and supervisors. To be well-accepted, QC should be practical and workable and should not overload the laboratory.
Every component of the laboratory workflow should be checked to guarantee a good laboratory result:
‒ laboratory arrangement
‒ human resources
‒ laboratory equipment
‒ collection and transport of specimens
‒ handling of specimens
‒ reagents and media
‒ culture procedure
‒ reporting of results.
Laboratory arrangement and administration
The main QA requirements for laboratory arrangement and administration are the following:
• Doors in the laboratory shouldalways be closed.
• Work areas, equipment and supplies should be arranged for logical and efficient work-flow.
• Work areas should be kept clean and free of dust.
• Benches should be swiped at least once a day with an appropriate disinfectant.
• Standard Operating Procedures (SOPs) should be used. Laboratory procedures used routinely should be those that have been published in reputable microbiological textbooks, manuals or journals.
• Written procedures must be kept in the laboratory for easy reference. Any changes must be dated and initialled by the laboratory supervisor.
• All records should be retained for 2 years.
Human resources
Trained health staff are crucial to ensure high-quality laboratory services. A well-planned training programme should be in place in each laboratory and new personnel should be trained before starting work. Staff competency should be reviewed annually, and retraining should be considered if results from QA programmes are not satisfactory Appropriate records (such as that shown in Figure 1 as an example for the NTP) should be filled in and maintained.
Specific retraining of laboratory staff on cultures should be considered when problems in culture procedures have been detected (see “Daily monitoring routine” and “Periodic monitoring routine” below for further details).
Numbers of laboratory workers should be sufficient to avoid staff shortages and excessive workloads.
Figure 1. Staff training form
Laboratory equipment
All laboratory equipment should meet the manufacturers’claims and specifications, and written operating and cleaning instructions must be kept in a file, together with the dated service records. Equipment must be monitored regularly to ensure constant accuracy and necessary precision. The particular requirements for each instrument must be strictly observed.
Biological safety cabinet
It is important to check the airflow daily: it should never be lower than 0.38 -0.51 metre/second (75 -100 linear feet/minute) depending on the BSC (sub)classification. The magnehelic gauge in the exhaust duct should also be checked for any pressure drop across the filters: replace the filters when the gauge indicates that the airflow across the front opening hasdropped below optimal levels.
At the time of installation and annually thereafter, the performance of the BSC should be certified by a professional to ensure laboratory safety. Re-certification should include tests for cabinet integrity, HEPA filter leaks, downflow velocity profile, face velocity, negative pressure/ventilation rate, air-flow smoke pattern, and alarms and interlocks. Optional tests for electrical leaks, lighting intensity, ultraviolet light intensity, noise level and vibration may also be conducted.
Airflowsmoke patterns tests are performed to determine whether the airflow along the entire perimeter of the work access opening is inward, whether airflow within the work area is downward with no dead spots or refluxing, whether ambient air passes onto orover the work surface, and whether there is refluxing to the outside at the window wiper gasket and side seals. The smoke test is an indicator of airflow direction, not of velocity. Commercial airflow testers are recommended. They are small glass tubes, sealed at each end. Both ends are broken off with the tool provided and a rubber bulb is fitted to one end. Pressing the bulb to pass air through the tube causes it to emit white smoke.
The down-flow velocity and volume test measures the velocity of air moving through the cabinet workspace.
The inflow velocity test is performed to determine the calculated or directly measured velocity through the work access opening, to verify the nominal set point average inflow velocity and to calculate the exhaust airflow volume rate. An electronic vane-type anemometer should be used to measure airflow.In Class II cabinets, the airflow is greater at the bottom than at thetop of the working face. The average inward flow is calculated by measuring the velocity of air leaving the exhaust and the area of the exhaust vent. From this the volume per minute is calculated, which is also the amount entering the cabinet. Divided by the areaof the working face it gives the average velocity. The downward velocity of air should be measured at 18 points in the horizontal place, 10 cm above the top edge of the working face. No reading should differ from the mean by more than 20%.
The HEPA filter leak test is performed to determine theintegrity of supply and exhaust HEPA filters, filter housing, and after-mounting frames while the cabinet is operated at the nominal set point velocities. An aerosol in the formof generated particulates of dioctylphthalate (DOP) or an accepted alternative is required for leak-testing HEPA filters and their seals. Although DOP has been identified as apotential carcinogen, competent service personnel are trained to use this chemical in asafe manner. The aerosol is generated on the intake side of the filter, and particles passing through the filter or around the seal are measured with a photometer on thedischarge side. This test is suitable for ascertaining the integrity of all HEPA filters.
The cabinetleak test is performed to determine whether exterior surfaces of all plenums, welds, gaskets, and plenum penetrations or seals are free of leaks. It is performed just before initial installation when the BSC is in a free-standing position in the room in which it will be used, after a cabinet has been relocated to a new location, and again after removal of access panels to plenums for repairs or a filter change. This test may also be performed on fully installed cabinets.
The electrical leakage and ground circuit resistance and polarity tests determine whether a potential shock hazard exists by measuring the electrical leakage, polarityground fault interrupter function, and ground circuit resistance to the cabinet connection. The polarity of electrical outlets is checked using a polarity tester. The ground fault circuit interrupter should trip when approximately 5 mA isapplied.
The noiselevel test is performed to measure the noise levels produced by the cabinet, as a guide to satisfactory mechanical performance (should be <59 db).
Centrifuge
Check brushes and bearings every 6 months (for more detailed requirements see Module 3 on laboratory equipment)
Incubator 35–37 °C
Record the temperature daily, preferably in the morning, in the appropriate form (see the example in figure 2). Test the temperature at several sites within theincubator by placing a thermometer in a water reservoir (e.g. Erlenmeyer flask). Control the light within the incubator by covering the glass front of the incubator door and restricting the use of any lights inside the incubator.
Inspissator
Check the temperature daily and clean after preparation of each batch of culture media.
pH meter
Compensate for temperature with each run. Date buffer solutions and discard when unsatisfactory. Standardize with pH 4.0, 7.0 and 8.0 or 10.0 buffers before each test or series of tests.
Balance
The minimum requirement is a twin-beam balance weighing up to 200 g with a precision of ±0.1 g. The maximum load of the scale must not be exceeded. Make sure that the balance is placed on a clean, level, stable, vibration- and draught-free surface. To ensure accurate weighing, recalibrate the balance periodically with reference weights.
Water-baths
Check temperature before and during use. Clean monthly.
Refrigerators 2–8 °C
Record the temperature daily, preferably in the morning, in the appropriate form (see the example in figure 2). Clean monthly. Defrost or check refrigerator and freezer compartment every 3 months.
Freezer
Record the temperature daily, preferably in the morning, in the appropriate form (see the example in figure 2). Clean every 6 months.
Glassware
Discard chipped or etched glassware. Ensure that glassware is free of detergents. Do not store sterile glassware for more than 3 weeks before it is used.
Records
All checks should be recorded. The record form should include: the name of the instrument, the expected range of the checked characteristic (e.g. for checking the temperature of an incubator, state that the expected range is 35–37 °C), the date, the recorded value of the particular characteristic and the signature of the person in charge of the check. If the noted characteristic is out of range, this should be recorded, together with the corrective actions taken.
Completed forms should be kept for 2 years.
Collection and transport of specimens
Samples should always carry clear identification and be accompanied by a properly completed NTP request form. Reject specimens that cannot be properly identified and do not allow oral requests without follow-up written instructions. Insist onspecimen request forms being kept separate from the specimens themselves: forms that have been contaminated by specimens should be sterilized by autoclaving.
It is crucial for the laboratory to be able to differentiate specimens received for diagnostic purposes from those received for control of treatment. This allows proper interpretation of results and guides the sequence of bacteriological studies needed for each patient. Lack of this information means that monitoring of bacteriological results cannot be used as a method of quality control.
Evaluate the quality of sputum specimens and make a note if any specimen resembles saliva. The report should state “specimen resembling saliva – consider a negative result with caution”. Discard leaking and broken specimen containers after autoclaving and request repeat specimens. Document the time of arrival of specimens in the laboratory and note any delays in delivery on the reportform, particularly in the case of negative/contaminated results
In addition, make sure that the laboratory register contains the date on which samples were cultured as well as any relevant details concerning their processing, e.g. decontamination of aseptically collected specimens.
Figure 2. Temperature record form
TEMPERATURE REQUIRED: 36 ± 1 °C (acceptable variation)
Trimester:
/Year :
Month
------/Temp.
°C / VisaInitials /
Month
------/Temp.
°C / VisaInitials /
Month
------/Temp.
°C / VisaInitials
1 / 1 / 1
2 / 2 / 2
3 / 3 / 3
4 / 4 / 4
5 / 5 / 5
6 / 6 / 6
7 / 7 / 7
8 / 8 / 8
9 / 9 / 9
10 / 10 / 10
11 / 11 / 11
12 / 12 / 12
13 / 13 / 13
14 / 14 / 14
15 / 15 / 15
16 / 16 / 16
17 / 17 / 17
18 / 18 / 18
19 / 19 / 19
20 / 20 / 20
21 / 21 / 21
22 / 22 / 22
23 / 23 / 23
24 / 24 / 24
25 / 25 / 25
26 / 26 / 26
27 / 27 / 27
28 / 28 / 28
29 / 29 / 29
30 / 30 / 30
31 / 31 / 31
Handling of specimens
The routine of laboratory work will determine the maximum possible number of days per week that can be allocated to specimen processing. Each day of delay in the inoculation of a specimen on growth media diminishes culture positivity rate: processing of the specimens should not be delayed for more than 7 days following collection. When transportation delays are expected, use commonly recommended preservative methods, such as the cetylpyridinium chloride/NaCl method. This method not only reduces the number of cultures lost to contamination but also significantly reduces the laboratory time required for processing specimens. The processing of gastric lavage specimens from children should be expedited as much as possible.