Gisborne Hospital Report - Health and Disability Commissioner

More documents

Recommendations

Info

Gisborne Hospital 1999 – 2000 PSA Testing Procedures Purpose of quality control 2.4 Quality control is used to check that all aspects of the analytical processes being used by a laboratory are functioning properly. The overall purpose is to ensure that the patient’s test results are as reliable as practically possible. 2.5 There are many aspects to quality control. These include routine maintenance and calibration of the instruments, checking and recording batch numbers of reagents, controls and calibration material, as well as using internal and external quality control samples to check the accuracy and precision (reliability) of the method being used to test patient specimens. 2.6 The problems with the PSA measurements at Gisborne Hospital relate predominantly to a failure to check that the correct calibrators were being used, the incorrect interpretation and response to unexpected internal and external quality control results that detected this error, and the lack of an external control programme as a final check on test reliability. Control samples 2.7 Internal and external quality control programmes involve the measurement of analytes in control samples. These control samples are available commercially, in liquid, frozen or lyophilised form, and are packaged in small bottles for daily usage. When reconstituted, they resemble the patient samples as closely as possible, except that they contain known concentrations of the analytes being measured. For example, the PSA concentration in patients is measured in a sample of their serum (blood with the red cells removed). The control material used will resemble serum, but will have been spiked to provide a known concentration of PSA. This concentration will be noted on the control bottle label or on the leaflet inserted into the package containing the bottle of control material. 2.8 It is common practice to use at least two internal control samples containing different concentrations of the analyte being measured. This checks the validity of results across the range of concentrations one is likely to measure in patient specimens. Internal quality control samples 2.9 Internal quality control samples are measured in parallel with the patient specimens, with the concentration measured in the control samples being expected to fall within pre-defined limits, close to the known and stated values. These limits allow for acceptable variation in the precision of the measuring system, but are always much less than the degree of variation that could be clinically significant in the accompanying patient specimens. 2.10 If, for example, the value obtained for the PSA internal control samples did not fall within the acceptable limits, then the accompanying patient test results should be discarded. There are a range of procedures that the technologist 137
Gisborne Hospital 1999 – 2000 PSA Testing Procedures should then carry out to determine and rectify the cause of the out of control measuring system, before attempting to repeat the tests. 2.11 Internal quality control samples are often provided by the manufacturer of the instrument and/or reagents being used, although suitable control samples are also often available from an alternative manufacturer. There may be advantages in using an alternative source for control samples, as an independent check on the instrument or reagent manufacturer’s system. Alternative material is also sometimes cheaper, more stable, or may contain other analytes which can be used to check other tests carried out in the laboratory. The use of an alternative source for internal control samples, as used for PSA at Gisborne Hospital, is an acceptable practice. 2.12 The error made at Gisborne Hospital was that the stated values for PSA for the internal control samples were changed to fit the results obtained when the wrong calibrator was used. The wrong internal control result should have alerted them to an analytical system error and led to a series of procedures that would eventually have located the cause of the abnormal control results. 2.13 Internal control samples are analysed frequently to ensure that the analytical process is under control at all times. Because the internal control values were altered at Gisborne Hospital, the error introduced into patient specimen results, as a result of incorrect calibrators being used, remained undetected until a locum technologist recognised the error. 2.14 There is reference later in this chapter to the use of rules for determining whether the values obtained on internal quality control samples indicate that the patient results should be accepted or rejected. There are a number of statistical techniques, of varying complexity, for doing this. The Westguard rules and Levey-Jennings plots used at Gisborne Hospital are commonly used. These techniques were applied by entering the internal quality control sample results into a software programme (QC Reporter 2.0). 2.15 The reason that rules are used to decide on rejection or acceptance of results, rather than immediate rejection if one of the control results is not exactly right, is that there is an unavoidable variation in the precision of all steps employed as part of the testing process. This in turn produces an unavoidable variation in the final control results. The rules are used to decide when this variation is excessive and clinically unacceptable, and thus alerts the technologist to problems with the instrument or method. 2.16 It is essential that the internal quality control results are checked before the patient results are reported, as an unacceptable performance should cause those results to be discarded. Although the rules for acceptance or rejection of results used at Gisborne Hospital were applied correctly, the internal control results were not entered into the QC Reporter 2.0 programme until after the patient results had been reported, and thus failed to fulfil their primary purpose. External quality assurance programmes 138
Page 1 and 2:
GISBORNE HOSPITAL 1999 - 2000 A rep
Page 3 and 4:
Table of Contents Page Executive Su
Page 5 and 6:
1. BACKGROUND EXECUTIVE SUMMARY 1.1
Page 7 and 8:
3. THE ENVIRONMENT 3.1 My investiga
Page 9 and 10:
pathologist, staff shortages and pr
Page 11 and 12:
Gisborne Hospital 1999 - 2000 Intro
Page 13 and 14:
Page 15 and 16:
Page 17 and 18:
Page 19 and 20:
Page 21 and 22:
Page 23 and 24:
Page 25 and 26:
Page 27 and 28:
Page 29 and 30:
Chapter 2 Quality Assurance Systems
Page 31 and 32:
Gisborne Hospital 1999 - 2000 Quali
Page 33 and 34:
Page 35 and 36:
Page 37 and 38:
Page 39 and 40:
Page 41 and 42:
Page 43 and 44:
Page 45 and 46:
Page 47 and 48:
Page 49 and 50:
Page 51 and 52:
Page 53 and 54:
Page 55 and 56:
Page 57 and 58:
Gisborne Hospital 1999 - 2000 Incid
Page 59 and 60:
Page 61 and 62:
Page 63 and 64:
Page 65 and 66:
Page 67 and 68:
Page 69 and 70:
Page 71 and 72:
Page 73 and 74:
Page 75 and 76:
Page 77 and 78:
Gisborne Hospital 1999 - 2000 Opera
Page 79 and 80:
Page 81 and 82:
Page 83 and 84:
Page 85 and 86:
Page 87 and 88:
Page 89 and 90:
Page 91 and 92:
Page 93 and 94:
Page 95 and 96: Gisborne Hospital 1999 - 2000 Opera
Page 145: Gisborne Hospital 1999 - 2000 PSA T
Page 149 and 150: Gisborne Hospital 1999 - 2000 PSA T
Page 183 and 184: Gisborne Hospital 1999 - 2000 Patie
Page 189 and 190: RECOMMENDATIONS Quality Assurance S
Page 191 and 192: Gisborne Hospital 1999 - 2000 Recom
Page 193 and 194: Gisborne Hospital 1999 - 2000 Recom
Page 195 and 196: APPENDIX NZNO LETTER TO MINISTER OF
Page 197 and 198:
11. The anaesthetist had a practice
Page 199 and 200:
THE ANONYMOUS LETTER The anonymous
Page 201:
GLOSSARY ABBREVIATIONS A&E A,T&R AQ
show all

Gisborne Hospital Report - Health and Disability Commissioner

Create successful ePaper yourself

Delete template?

Save as template?