Laboratory Calibration Workshop Notes

Setting and Focus

• Pathology Laboratory: The workshop is set in the context of a pathology laboratory.
• Focus: The primary focus is on the maintenance, service, repair, check, and calibration of laboratory equipment to ensure its performance.

Scope

• Overview: The workshop provides an overview with references for more detailed information.
• Australia’s Peak Bodies and Standards: It covers Australia's peak bodies and standards related to laboratory equipment.
• Performance Management: It includes an overview of performance management for main laboratory equipment.
• General Equipment: The workshop discusses various types of general laboratory equipment, including:
  • Laboratory Timer
  • Centrifuge
  • Pipette
  • Balance
  • Digital Thermometer
  • Fridge
  • Freezer
  • Incubator
  • Water Bath
  • Heating Block

Key Organizations

• Standards Australia:
  • Australia's peak non-government, not-for-profit standards organization.
  • Website: https://www.standards.org.au/
• National Pathology Accreditation Advisory Council (NPAAC):
  • Ensures the quality of Australian pathology services.
  • Responsible for the development and maintenance of standards and guidelines for pathology practices.
  • Website: National Pathology Accreditation Scheme | Australian Commission on Safety and Quality in Health Care
• National Association of Testing Authorities, Australia (NATA):
  • Australia’s national accreditation body for laboratories, inspection bodies, calibration services, producers of certified reference materials, and proficiency testing scheme providers.
  • Website: https://www.nata.com.au/

Equipment Requirements

• S7B.5 Requirement: "Equipment must be “fit for purpose” and must be maintained to ensure functionality."
  • Source: REQUIREMENTS FOR MEDICAL PATHOLOGY SERVICES (Third Edition 2018)

Laboratory Equipment Records (AS ISO 15189:2023)

• 6.4.7 Equipment records shall be maintained for each item of equipment that influences the results of laboratory activities. These records shall include the following, where relevant:
  • a) Manufacturer and supplier details, and sufficient information to uniquely identify each item of equipment, including software and firmware.
  • b) Dates of receipt, acceptance testing, and entering into service.
  • c) Evidence that equipment conforms with specified acceptability criteria.
  • d) The current location.
  • e) Condition when received (e.g., new, used, or reconditioned).
  • f) Manufacturer's instructions.
  • g) The program for preventive maintenance.
  • h) Any maintenance activities performed by the laboratory or approved external service provider.
  • i) Damage to, malfunction, modification, or repair of the equipment.
  • j) Equipment performance records such as reports or certificates of calibrations or verifications, or both, including dates, times, and results.
  • k) Status of the equipment such as active or in-service, out-of-service, quarantined, retired, or obsolete.
• These records shall be maintained and shall be readily available for the lifespan of the equipment or longer, as specified in 8.4.3.

Equipment Maintenance and Repair

• Equipment shall be maintained in a safe working condition and working order. This includes electrical safety, emergency stop devices, and the safe handling and disposal of hazardous materials by authorized personnel.
• Equipment will have:
  • A standard operating procedure.
  • A record of maintenance.
    • Daily: Flushing the lines of the instrument, ensure no residual reagent is left on probes or surfaces.
    • Weekly
    • Monthly
    • Preventive maintenance: Usually performed by the instrument supplier.

Laboratory Analysers, Point-of-Care Analysers

• Training: Provided by the supplier/company for laboratory staff for different levels of maintenance (e.g., daily, weekly, monthly, 3-monthly).
• Preventive Maintenance: Likely to be performed 6-monthly (and/or annually) by trained company technicians and may involve replacing parts.
• Records Retention: Records must be retained for the life of the analyzer + 4 years (NPAAC Requirements for the retention of Laboratory Records and Diagnostic Materials (2018)).
• Record Format: Records may be electronic or paper and must be available for review at NATA assessments.

Equipment Maintenance Details

• Service: May be carried out when there is a problem that occurs outside of the maintenance schedule. It may also involve replacing faulty parts. A service report is required to be issued by the service provider (usually the supplier of the analyzer) and retained as per NPAAC requirements.
• Checks: For analyzers, usually involve running Quality Control materials through to ensure the QC results are within an acceptable range.
• Calibrations: Are required at regular intervals, and the type of calibration may be different depending on the type of analyzer. Calibrators/materials for calibrations are usually provided by the supplier.

Analyser Daily & Weekly Maintenance Checklist

• Example checklist emphasizing daily and monthly maintenance tasks for Phadia 250 instrument.
• Includes tasks such as cleaning probes, overflow cells, mixing reagents, and performing rinses with MilliQ water.
• Monthly cleaning involves using cleaning solutions and hypochlorite solutions, with specific instructions for preparation and usage.
• Cleaning processing units includes scrubbing the Immuno Reaction Wheel and cleaning various components with alcohol wipes.

Calibration Importance

• Equipment checks are part of an equipment assurance program and are performed to determine that an item has not deviated significantly from its original value or in between calibrations and verifications.
• Checks are assessed for competency during a NATA visit; the additional criteria in this policy do not apply to checks in this context.

Equipment Calibration Procedures

• 6.5.2 Equipment calibration The laboratory shall have procedures for the calibration of equipment that directly or indirectly affects examination results. The procedures shall specify:
  • a) Conditions of use and manufacturer's instructions for calibration.
  • b) Recording of the metrological traceability.
  • c) Verification of the required measurement accuracy and the functioning of the measuring system at specified intervals.
  • d) Recording the calibration status and date of re-calibration.
  • e) Ensuring that, where correction factors are used, these are updated and recorded when recalibration occurs.
  • f) Handling of situations when calibration was out of control, to minimize risk to service operation and to patients.

Traceability

• Metrological traceability shall be to a reference material or reference procedure of the higher metrological order available.
• NOTE Documentation of calibration traceability to a higher order reference material or reference procedure may be provided by an examination system manufacturer. Such documentation is acceptable as long as the manufacturer's examination system and calibration procedures are used without modification.
• Where this is not possible or relevant, other means for providing confidence in the results shall be applied, including but not limited to the following:
  • use of certified reference materials;
  • examination or calibration by another procedure;
  • mutual consent standards or methods which are clearly established, specified, characterized and mutually agreed upon by all parties concerned.

Why Calibrate?

• Improved trueness occurs when the center of the cluster is closer to the center of the target.
• Improving precision brings the cluster of the results into a smaller bunch.
• Accuracy is improved by improving trueness and precision.
• Trueness, precision, and accuracy are conceptual terms.
• Quantitative expressions of these concepts are given in terms of systematic error, random error, and uncertainty, respectively.

Systematic Error, Random Error & Measurement Uncertainty

• Systematic error is estimated by the deviation of the measured mean volume from the target volume.
• Random error of a channel is usually assessed by calculating the standard deviation of a series of N measured volumes under repeatability conditions.
• The measured volume is an estimate of the delivered volume and departs slightly from the true delivered volume due to measurement uncertainty (MU). Measurement uncertainty reflects the fact that no measurement is perfect.

Calibration Services

• Calibration Laboratory
  • pH meter timers
  • Calibration service
• External services
  • Centrifuges
  • Fridges and freezers
  • Pipettes
  • Balances
  • Thermometers
  • Spectrophotometer calibration
  • Instruments dispensing fixed volumes

Checks

• 'Check' is a measurement of at least one point in a range of a measuring instrument or system or material against a known value to confirm that it has not deviated significantly from its original calibrated value. It is also an examination of the condition of an artifact, i.e., the reference of known value, to determine that it has not been adversely affected by constant use.
• By performing a check on an instrument, a facility can determine if the instrument has changed since its last calibration. By performing regular checks, the interval between periodic calibrations may be extended.
• Equipment checks are part of an equipment assurance program and are performed to determine that an item has not deviated significantly from its original value or in between calibrations and verifications.

Piston-Operated Volumetric Apparatus (POVA)

• ISO 8655-1:2022 (E)
• Routine testing of the POVA shall be performed at regular intervals as part of test equipment monitoring or analytical quality control routines, for example, every three months (see 6.1). Other time intervals may be adopted giving due consideration to the following factors:
  • risk of application;
  • frequency of use;
  • number of users of the POVA;
  • aggressive nature of the liquid to be delivered and its vapors;
  • acceptable maximum permissible errors;
  • manufacturer's information;
  • number of dispenses performed on each occasion of use;
  • liquid handling process requirements.
• The determination of the delivered volume shall be done following the procedures specified in ISO 8655-6 and ISO 8655-8, or by the adoption of other methods in accordance with ISO 8655-7.

Pipette Calibration Details

• Gravimetric Methods for the Determination of Measurement Error
  • Pure Water - 1g = 1ml = 1000\mu l
• Purpose-built POVA (Piston-Operated Volumetric Apparatus) calibration facility
• Conforms to apparatus (balance, evaporation trap, weighing table, mass, test liquid) and environmental (barometric pressure, humidity and temperature) requirements specified in ISO 8655:2002.
• The number of times a POVA is calibrated per year mainly depends on the number of times the POVA is used, the number of users, the nature of the liquid dispensed, and the quality standards of the laboratory.

Pipette Testing Plan

• Fixed volume pipettes are tested at nominal volume.
• Variable volume pipettes are tested at three different volumes – nominal volume, at approximately 50% and 10% of the nominal volume or lower limit of the useful volume range (whichever is greater).
• Multi-channel pipettes are tested for each channel. Each channel shall be regarded as a single channel and tested and reported as such.
• 10 measurements for each test volume shall be carried out. These measurements are used to calculate the systematic and the random error of measurement.
• The maximum permissible error applies to the total system of piston pipette and tip.

Relevant ISO Standards for Pipettes

• ISO 8655-1:2002 POVA - Terminology, General Requirements & User Recommendations
• ISO 8655-2:2002 POVA - Piston Pipettes
• ISO 8655-6:2002 POVA - Gravimetric Methods for the Determination of Measurement Error

Laboratory Timer Calibration

• Traceable Reference Time – NMI WebTimer (https://webtimer-syd.nmi.gov.au)
  • A simple and convenient service developed by the Time and Frequency Standards team at the National Measurement Institute (NMI).
  • Make time interval measurements that are traceable to the Australian primary standard for time.
  • The NMI WebTimer is a browser-based service that provides a measurement of the time interval between two clicks of a button on a user’s computer (including mobile devices). It calculates and reports the measurement uncertainties on-screen. Users are able to print and save a report of their time interval measurement that documents uncertainties and traceability to UTC(AUS) – Australia’s realization of Coordinated Universal Time (UTC).
  • NATA recommends timers be checked on a 6-month cycle.
  • NATA recommends that stopwatches be checked every 6 months by comparison with a reference that is traceable to the national standard. NTP is suggested as a way of satisfying this.

Timer Calibration Test Procedure

• Fill in the stopwatch or timer’s asset number, equipment ID, or serial number in the WebTimer’s comments box if required.
• Select a computer and access https://www.time.gov/ via a standard desktop web browser. Ensure that the “Off by” is less than 0.5 s. If not, find another computer that meets this requirement.
• For a countdown timer, set the timer to 4:00:00.
• Click “Start” on the WebTimer and start the stopwatch or timer simultaneously.
• Record the WebTimer’s displayed local time (in hh:mm:ss) in column (A) and the stopwatch or timer start time (in hh:mm:ss) in column (D) on recording form CAL-F911.
• After a minimum of 3 hours, click “Stop” on the WebTimer and stop the stopwatch or timer simultaneously.
• Record the WebTimer’s displayed local time (in hh:mm:ss) in column (B) and the stopwatch or timer stop time (in hh:mm:ss) in column (E) on recording form CAL-F911.
• Record the WebTimer’s “Uncertainty due to the Network Delay” on recording form CAL-F911.
• Subtract the WebTimer’s traceable reference start time from the stop time to get the reference time interval, and compare this reference time interval to the time interval displayed by the stopwatch or timer.
• The two-time intervals must agree to within the tolerance specifications (≤ 2 s) for a successful calibration.
• If the difference of the two time intervals is greater than 2 s, replace the battery in the stopwatch or timer with a new battery and re-test. If calibration fails again, the stopwatch or timer shall be rejected.

Timer Calibration Specifications/Calculations

• Traceable Time Source (Reference)
  • Start Time (hh:mm:ss) – (A)
  • Stop Time (hh:mm:ss) – (B)
  • Time Interval (s) – C = B - A
• Digital Stopwatch / Timer (DUT)
  • Start Time (hh:mm:ss) – (D)
  • Stop Time (hh:mm:ss) – (E)
  • Time Interval (s) – F = |E - D|
• Time Interval Difference (s)
  • Time Interval Difference – |C - F| \le 2 s

Timer Calibration Acceptance Criteria/Standards

• A stopwatch or timer is considered to be within tolerance if its Time Interval Difference is 2 s or less during a three-hour calibration.
• Three hours is a long enough time interval to exceed the 0.02 % measurement uncertainty requirement to ensure that the uncertainty contribution of human reaction time is insignificant.
• Total Uncertainty of Measurement = \sqrt{U{nd}^2 + 2 \cdot U{ts}^2 + 2 \cdot U_{sm}^2}
  • Where:
    • U_{nd} - Uncertainty due to the network delay
    • U_{ts} - Uncertainty components of time stamping
    • U_{sm} - Uncertainty to allow for the stopwatch and the mouse not being started or clicked at the same time
• Total Expanded Uncertainty of Measurement = k \times \text{Total Uncertainty of Measurement}
  • Where:
    • k = 2, representing approximately a 95 % level of confidence
• Laboratories are required to establish their acceptance criteria or specifications within their applications, processes, and requirements for the Total Expanded Uncertainty of Measurement.
• As an indication, an Uncertainty due to the network delay (U_{nd}) of 0.824 s would result in 1 s of Total Expanded Uncertainty of Measurement.

Timer Calibration Traceability

• Illustrates the traceability of network time to UTC(AUS) and typical uncertainties in the traceability chain.
• Expanded uncertainty of the link between NMI's remote NTP servers and UTC(AUS) is approximately \pm 50 ns

Centrifuge Checks

• Rotational speed, temperature, and timing.
• Use calibrated tachometer, thermometer, and timer.
• Checked 12-monthly.
• Establish laboratory permissible errors (inaccuracies).

Incubators/Digital Thermometers/Heat Blocks

• Ice Point (6-monthly) Check – ice slurry is the most convenient and gives a reproducible temperature when properly prepared.
• Working Temperature (annually) Check – using:
  • Calibrated Dry Block Calibrator
  • Water Bath with calibrated Reference Thermometer
  • In-situ with calibrated Reference Thermometer
• Permissible error and correction factor determined by laboratory.

Digital Thermometer Temperature Check

• Correction Factor for the thermometer being calibrated is calculated by subtracting its observed temperature from the true temperature of a calibrated Reference Thermometer.
• True temp of Ref Thermometer = Observed Temp + Correction factor
• Buffered Temperature Probe
• Essential part of a refrigerator/freezer temperature monitoring system that assures temperature readings meet audit guidelines.
• Avoid out-of-specification temperatures. Prevents false temperature alerts when the refrigerator or freezer door is opened and during defrost cycles.
• Ethylene Glycol is the preferred thermal buffer because it has a low freezing temperature.

Temperature Charts

• Examples of Equipment Temperature Charts used for monitoring and recording temperature readings in enclosures such as incubators and refrigerators.
• Include details such as enclosure ID, department, description, location, and allowable temperature range.
• Also include thermometer ID, correction factor, and spaces for recording daily temperature readings, initials, and comments.

Fridge, Freezer, Incubator, Water Bath, Heating Block

• AS2853-1986 - Enclosures - Temperature Controlled - Performance Testing and Grading
• Applies to the unloaded condition under either steady-state or dynamic modes of operation.
• Spatial variation - difference between the midrange of all measured temperatures obtained at one site and that at another site for those sites which give the greatest difference.
• From a qualification perspective, the empty mapping would occur in the Operational Qualification phase, and the loaded chamber would occur in the Performance Qualification phase.

Worksheet Tasks

• Record the weights for the pipette calibration and the object provided.
• Calculate the mean and standard deviation of the repeated measures.
• Determine if they pass or fail.
• Work through the worksheet using the references provided.