Laboratories to review procedures
25 August 2005
Laboratories to review procedures
The Ministry of Health's National Screening Unit has asked laboratories to review their procedures following a processing error affecting lab samples taken from 37 Gisborne women in the past three months.
The 37 women, all from the Tairawhiti region, are being recalled for repeat cervical smears following the identification of a laboratory collection and processing error. All of the women have been contacted by their General Practitioners to arrange for a repeat smear at no cost to the women.
The error occurred when an incorrect method was used to process smears collected using a new product, that may result in the smear results being unreliable.
Karen Mitchell, Group Manager of the National Screening Unit (NSU), says that the risk for women is very small due to early identification and prompt action by the laboratories and GPs, however it is important to ensure the error does not occur again.
International Accreditation New Zealand (IANZ) is working with the NSU to undertake an investigation into how the error occurred. The NSU has also written to all laboratories contracted to provide cytology screening services asking them to review their collection and processing procedures, particularly in relation to the use of new products.
A woman?s best protection against developing cervical cancer is having regular cervical smear tests. The National Cervical Screening Programme recommends cervical smear tests every three years for women from the age of 20 until they turn 70.
Any woman with concerns is encouraged to contact her doctor or smear taker.
How many women were affected? Cervical samples from 37 women were affected. All 37 women will be rescreened.
Who pays for the repeat smear? The cost of the repeat smears will be met by Southern Community Laboratories.
What was the technical fault? The smear samples (of cells taken from a woman's cervix) were collected using equipment and solutions provided by one manufacturer (SurePath) and then processed by using a different manufacturer's products (ThinPrep). Although the technology used by the two firms are similar, both manufacturers advise against doing this. Once the error was recognised, the samples were traced and medical practices and women alerted to what had happened.
What are SurePath and ThinPrep? They are two commercial methods for preparing cervical smears using a liquid based technology. The traditional method of smear preparation to screen for cervical cancer is the Pap smear where a sample of cells from an individual's cervix is collected, spread thinly on a glass slide, stained and then examined under a microscope for unusual cells. Liquid based cytology involves taking a similar sample, mixing that in liquid and then processing in a machine to provide sample cervical cells on a glass slide to be examined under a micropscope.
What is the difference between SurePath and Thin Prep? The two liquid based technologies used in NZ, ThinPrep and SurePath, use different fixatives in their collection vials. The validation studies performed on each system are based on specimens processed only with the appropriate fixative solutions. The manufacturers recommend that the collection vials and processing systems are not able to be mixed and results obtained from processing specimens in this way have not been validated and may be unreliable.
How common is liquid based cytology in New Zealand? Based on a survey by the NCSP done late last year, the NSU estimates that approximately a third of all cervical screening slides are examined using liquid based cytology.
What does the Ministry advise where the processes have been mixed by error? The Ministry believes that the steps being taken by the laboratories involved are appropriate, that is to invite those individuals whose samples were processed through a combination of SurePath and Thin Prep, to be rescreened.
What does rescreening involve? The individual women will be invited to have another cervical smear taken and have those processed and examined.
What risks are the individual women exposed to? The individual risk for women concerned is regarded as very small. Each of the 37 women were being screened as part of the standard screening process and the small delay (a maximum of three months) is not regarded as being clinically significant.
What processes are in place to prevent this happening again? The National Cervical Screening Programme has Operational Policy and Quality Standards for medical laboratories. In the Agreement with medical laboratories contracted by the National Screening Unit to provide cytology screening services, all medical laboratories are required to meet the relevant standards and be internationally accredited by IANZ. As part of that accreditation there is annual surveillance of the laboratory's performance and a three yearly audit. The NSU also audits each laboratory on a three yearly cycle. Six laboratories were audited by the NSU in the last financial year and the remaining four will be audited this year. There are a range of other standards and auditing processes for other parts of the screening pathway.
What does IANZ stand for? International Accreditation New Zealand. Accreditation is the recognition by an official accreditation body of appropriate standards. IANZ is the operational arm of the Testing Laboratory Registration Council (TELARC). IANZ is a non-profit and user-funded body. It is a New Zealand Crown entity reporting annually to Parliament and established by the Testing Laboratory Registration Act 1972.