UNCERTAINTY OF MEASUREMENT

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INTRODUCTION

To comply with UKAS Medical Laboratories – Requirement for Quality and Competence ISO 15189:2012 it is necessary to determine the uncertainty of results where relevant. Full consideration and awareness of all identifiable components that contribute to the uncertainty of a test will allow valid results to be obtained and may also indicate aspects of a test or procedure which need improvement.

Uncertainty of measurement is normally associated with a quantitative result. Although most results in Cellular Pathology are not quantitative, determining the possible errors during the processing of samples provides information on total error and creates the doubt (uncertainty) of the true validity of the result.

Cellular Pathology uses the evidence from the repeatability or reproducibility of a test where possible to meet this standard.

Please note that a negative cytology report does not exclude the presence of disease.

 

SOURCES OF UNCERTAINTY OF MEASUREMENT

There are two types of uncertainty as defined by the International Organization for Standardization.

Type A is the statistical figures for specific assays and includes:

• Calibration data
• Internal Quality Control statistics
• External Quality Assurance data
• Verification of data from implementation and evaluations

Type B is the non-statistical measures and can be grouped as:

• Pre-examination
• Examination
• Post-examination

 

FACTORS AFFECTING THE UNCERTAINTY OF MEASUREMENT

The following factors can all affect the quality of results in Cellular Pathology:

• Specimen collection procedures including sample quality
• Transportation of samples
• Storage facilities for samples prior to testing
• Quality of reagents and consumables
• Performance of equipment
• Distribution of normal/abnormal cells in an aliquot of sample
• Technical competence of staff undertaking the testing
• Reporting protocols
• Referral of samples to other laboratories for testing

In order to minimize the uncertainty of measurement, all of these factors must be evaluated, monitored and where possible actions taken to minimize them.

 

MONITORING AND MINIMIZING UNCERTAINTY OF MEASUREMENT

PRE-EXAMINATION
	LAB ACTIVITY TO MONITOR	LAB ACTIVITY TO MINIMIZE	RELATED STANDARDS ISO 15189
PATIENT STATE & PREPARATION	Ensure all relevant clinical information is supplied on EPIC and on request forms from external sources	Advice available from http://www.exeterlaboratory.com/ and the laboratory  at 01392 402991	5.4
SAMPLE COLLECTION TIME	Lab to note any samples not received promptly in lab	As Above	5.4
SPECIMEN COLLECTION AND HANDLING	Lab to log all sample and/or request form errors (Includes labelling, leakage and missing samples)	As Above	5.4
SAMPLE TRANSPORT	Delays due to transport logged	Transport policy on Intranet	5.4.5
THIRD PARTY	Ensure third party compliant with any registration or accreditation requirements	Annual review of referrals to third parties	4.5
SAMPLE & BODY STORAGE	Fridge temperature monitoring	Procedure in place for logging any incidents or equipment downtime	5.4.7

 

EXAMINATION
	LAB ACTIVITY TO MONITOR	LAB ACTIVITY TO MINIMIZE	RELATED STANDARDS  ISO 15189
CALIBRATION	Timely calibration of appropriate equipment	Ensure companies performing calibration comply with UKAS standards	5.3.1.4
INSTRUMENT PERFORMANCE	Error logging of equipment downtime	Preventative Maintenance and Servicing	5.3.1
REAGENTS	IQC & EQA monitored. Logged with lot numbers and expiry dates	Use of CE or UKCA marked reagents. All new methods verified prior to use	5.3.2
INTERNAL QUALITY CONTROL	All IQC checks documented in SOPs Stain quality Slide quality	Ensure all staff trained and competent for IQC Stain and slide checking for early recognition of any issues	5.6.2
EXTERNAL QUALITY ASSURANCE	Ensure laboratory enrolled in EQA or ILC schemes and relevant staff take part	Monitor EQA and ILC outcomes	5.6.2
STAFF COMPETENCY	Incidents and training issues logged and addressed	Training and competency updates for all staff Ensure staff comply with CPD requirements Retain training approval with IBMS	5.1
CONSUMABLES	Inspect and document consumables upon arrival to laboratory.	Avoid damaged consumables being used.	5.3.2.3

 

POST – EXAMINATION
	LAB ACTIVITY TO MONITOR	LAB ACTIVITY TO MINIMIZE	RELATED STANDARDS ISO 15189
REPORT	Avoid transcription errors prior to release of results Ensure correct patient management	Reports checked by qualified staff	5.8
INTERPRETATION	Ensure meaning of report is unambiguous	All reports checked by reporting Pathologist or AP	5.8
STORAGE, RETENTION AND DISPOSAL OF CLINICAL SAMPLES	Ensure compliance with current RCPath and HTA guidance	SOP in place for retention and disposal of clinical samples; audit procedures	5.7.2

Some individual tests have specific measurement uncertainty – please contact the laboratory for specific information 01392 402991.

 

Specimen Labelling Procedure