Summary of Results External Quality Assessment of Water Microbiology
Dialysis Water Scheme Distribution Number: DW13
Sample Numbers: DW13A, DW13B
Distribution Date: Results Due: Report Date:
July 2017 28 July 2017 15 August 2017
Samples prepared and quality control tested by:
Angela Appea Richard Borrill Thomas Harper Zak Prior Judith Spellar Aneta Stranc Lili Tsegaye
Data analysed by:
Joanna Donn Manchari Rajkumar
Report compiled by:
Joanna Donn Manchari Rajkumar
Authorised by:
Nita Patel
This report must not be reproduced without permission of the organisers. Public Health England Food and Environmental Proficiency Testing Unit (FEPTU) 61 Colindale Avenue London NW9 5EQ Tel: +44 (0)20 8327 7119 Fax: +44 (0)20 8200 8264 Email:
[email protected] The data in FEPTU reports is confidential
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For further information about the scheme please refer to: Scheme Guide: https://www.gov.uk/government/publications/food-and-water-proficiency-testing-schemes-scheme-guide Guide to Scoring and Statistics: https://www.gov.uk/government/publications/food-and-water-proficiency-testing-schemes-scoring-systems-and-statistics
General guidance for z-scores:
Participants’ enumeration results are converted into z -scores using the following formula: Z = (xi-Xpt) σpt
xi Xpt
= participants' result (expressed as a log 10 value) = assigned value (participants' consensus median (expressed as a log 10 value))
σpt
= the fixed standard deviation for the examination (calculated by FEPTU)
The σpt-value expresses the acceptable difference between the individual participant’s result and the participants’ consensus median. The σ pt-value used for calculating z-scores in the Dialysis Water Scheme is 0.35. A guide to interpreting z-scores follows, although laboratories must interpret their scores in the context of their own laboratory situation: z = -1.99 to +1.99 z = -2 to -2.99 or +2 to +2.99 z= < -3.00 or > + 3.00
satisfactory questionable unsatisfactory
It is usually recommended that z-scores exceeding ± 2.0 are investigated to establish the possible cause. As a general rule, PHE recommends that all questionable and unsatisfactory results are investigated. FEPTU Quality Control: To demonstrate homogeneity of the sample, a minimum of 10 LENTICULE® discs, selected randomly from a batch, are tested in duplicate for the enumeration test.
To demonstrate stability of the sample, a minimum of nine LENTICULE discs, selected randomly from a batch, are examined throughout the distribution period for the enumeration test. The FEPTU results are determined using a method based on ISO 13959:2014 - Water for haemodialysis and related therapies. The FEPTU results are used for guidance in the preliminary intended results notification, letters are posted on the website immediately after every distribution; electronic notification of their availability is sent to all participants. Refer to section 17.0 of the Scheme Guide if you have experienced difficulties with any of the examinations . https://www.gov.uk/government/publications/food-and-water-proficiency-testing-schemes-scheme-guide
Participants are reminded that reporting incorrect or false negative results for water samples could have serious public health implications. Participants who report unexpectedly high or low results for the enumerations on single occasions only should not be unduly alarmed, although they should still assess the reason(s) for the outlying result.
Please contact FEPTU staff for advice and information: Repeat samples
Carmen Gomes or Kermin Daruwalla
Data Analysis
Manchari Rajkumar or Nita Patel
Microbiological advice
Nita Patel or Zak Prior
General comments and complaints
Nita Patel or Zak Prior
Scheme consultants
Caroline Willis or Julie E. Russell
Scheme Co-ordinator
Nita Patel
Tel: +44 (0)20 8327 7119 Fax: +44 (0)20 8200 8264 Email:
[email protected] FEPTU's website
Accreditation: PHE Water EQA Scheme for Dialysis Water is accredited by the United Kingdom Accreditation Service (UKAS) to ISO/IEC 17043:2010.
0006
The data in FEPTU reports is confidential
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Sample: DW13A Contents:
Proteus mirabilis 4.0x10³ per disc (wild strain), Staphylococcus epidermidis 9 (wild strain)
Expected Results: All counts are expressed as colony forming units (cfu) per mL. The fixed standard deviation value (σpt value) used for calculation of the z-score is 0.35 for this parameter
Results FEPTU median (MF)¹
9
No. results returned
54
Assigned value (Participants' median all results)
10
Interpretation based on assigned value**
Satisfactory/Acceptable
Uncertainty of assigned value
1
Participants' mean (all results)
10
Expected Range
1 - 19
Standard deviation**
4
No of outlying counts
12
False positives
False negatives
0
Your result
Your interpretation
Score for performance assessment
Z-score
¹ Membrane filtration * Reference: http://ndt.oxfordjournals.org/content/17/suppl_7.toc section IV: Dialysis fluid purity ** Robust S* based on median absolute deviation about the participants’ median (MADe)
Total sent samples
64
Not examined
6
Non returns
3
The data in FEPTU reports is confidential
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Sample: DW13B Contents:
Aerococcus viridans 17 (wild strain)
Expected Results: All counts are expressed as colony forming units (cfu) per mL. The fixed standard deviation value (σpt value) used for calculation of the z-score is 0.35 for this parameter
Results FEPTU median (MF)¹
17
No. results returned
54
Assigned value (Participants' median all results)
14
Interpretation based on assigned value**
Satisfactory/Acceptable
Uncertainty of assigned value
1
Participants' mean (all results)
14
Expected Range
5 - 23
Standard deviation**
4
No of outlying counts
9
False positives
False negatives
2
Your result
Your interpretation
Score for performance assessment
Z-score
¹ Membrane filtration * Reference: http://ndt.oxfordjournals.org/content/17/suppl_7.toc section IV: Dialysis fluid purity ** Robust S* based on median absolute deviation about the participants’ median (MADe)
Total sent samples
64
Not examined
5
Non returns
3
The data in FEPTU reports is confidential
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Method based presentation DW13A : Total Viable Counts 17ºC - 23ºC for 7 days
FEPTU Method: Membrane Filtration
Method
Number of Results
Excluded Results
Percentage of the total
Median
Robust S*
Membrane Filtration
21
1
41
10
0
3
-
60
Not Stated
0
4
0
Other
0
0
0
Pour
22
2
43
10
0
1
-
60
Spread
8
0
15
Range Reported
DW13A - Total Viable Counts 17ºC - 23ºC for 7 days
61 55
cfu per mL
45
35
25
Participants' Median +3SD 23 Participants' Median +2SD 19
15 Participants' Median 10 5
Participants' Median -2SD 1 Participants' Median -3SD 1 7 9 52 89 97 115 126 157 166 183 226 271 532 782 791 933 1003 1010 1059 1083 1159 1163 1219 1227 1241 1358 1459 1500 1507 1614 1647 1773 1853 1893 1958 1965 1990 2018 2037 2058 2075 2101 2129 2142 2185 2200 2311 2316 2323 2380 2425 FEPTU QC Median
0
Laboratory identification number
Key: reported result by method Membrane Filtration
Not Stated
Other
Pour
Spread
The data in FEPTU reports is confidential
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Sample: DW13A Total Viable Counts 17ºC
Total Viable Counts 17ºC - 23ºC for 7
Total Viable Counts 17ºC - 23ºC for 7
- 23ºC for 7 days
days
days
Method
Media
Standard Method
Membrane Filtration
None
ISO 13959:2014
Membrane Filtration
Other
ISO 11663:2014
Membrane Filtration
R2A
European Renal Best Practice
Membrane Filtration
R2A
ISO 13959:2014
Membrane Filtration
TGEA
European Renal Best Practice
Count
1 1 1
Guidelines
7 1
Guidelines Membrane Filtration
TGEA
ISO 23500:2014
Membrane Filtration
TGEA
Other; please state
Membrane Filtration
TGEA
UK Renal Association Guidelines
Membrane Filtration
TSA
ISO 13959:2014
Membrane Filtration
YEA
Other; please state
Pour
Other
ISO 6222:1999
Pour
R2A
ISO 11663:2014
Pour
R2A
ISO 13959:2014
Pour
R2A
ISO 23500:2014
Pour
R2A
PHE guidelines
Pour
R2A
UK Renal Association Guidelines
Pour
TGEA
ISO 13959:2014
Pour
TGEA
PHE guidelines
Pour
YEA
European pharmacopoeia 5.0
Pour
YEA
ISO 13959:2014
Pour
YEA
ISO 6222:1999
Pour
YEA
Other; please state
Pour
YEA
UK Renal Association Guidelines
Spread
R2A
European pharmacopoeia 5.0
Spread
R2A
ISO 13959:2014
Spread
R2A
Other; please state
Spread
TGEA
European pharmacopoeia 5.0
Spread
TGEA
ISO 11663:2014
Spread
TSA
UK Renal Association Guidelines
Spread
YEA
PHE guidelines
The data in FEPTU reports is confidential
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1 2 2 1 1 1 3 2 3 2 1 1 1 1 1 3 1 4 1 2 1 1 1 1 1
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Method based presentation DW13B : Total Viable Counts 17ºC - 23ºC for 7 days
FEPTU Method: Membrane Filtration
Method
Number of Results
Excluded Results
Percentage of the total
Median
Robust S*
Membrane Filtration
22
0
41
14
0
0
-
45
Not Stated
0
5
0
Other
0
0
0
Pour
24
1
45
15
0
2
-
21
Spread
7
0
13
Range Reported
DW13B - Total Viable Counts 17ºC - 23ºC for 7 days
46
cfu per mL
40
30 Participants' Median +3SD 27 Participants' Median +2SD 23 20 Participants' Median 14 10 Participants' Median -2SD 5 Participants' Median -3SD 1 7 9 52 89 97 115 126 157 166 226 271 502 532 782 791 933 1003 1010 1059 1083 1159 1163 1219 1227 1267 1358 1459 1500 1507 1614 1645 1647 1773 1853 1893 1958 1965 1990 2018 2037 2058 2075 2101 2129 2142 2185 2200 2311 2316 2323 2380 2411 2425 FEPTU QC Median
0
Laboratory identification number
Key: reported result by method Membrane Filtration
Not Stated
Other
Pour
Spread
The data in FEPTU reports is confidential
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Sample: DW13B Total Viable Counts 17ºC
Total Viable Counts 17ºC - 23ºC for 7
Total Viable Counts 17ºC - 23ºC for 7
- 23ºC for 7 days
days
days
Method
Media
Standard Method
Membrane Filtration
R2A
European Renal Best Practice
Count
1
Guidelines Membrane Filtration
R2A
ISO 13959:2014
Membrane Filtration
R2A
ISO 23500:2014
Membrane Filtration
TGEA
European Renal Best Practice
Membrane Filtration
TGEA
ISO 13959:2014
Membrane Filtration
TGEA
ISO 23500:2014
Membrane Filtration
TGEA
Other; please state
Membrane Filtration
TGEA
UK Renal Association Guidelines
7 1 1
Guidelines
Membrane Filtration
TSA
ISO 13959:2014
Membrane Filtration
YEA
Other; please state
Pour
Other
ISO 6222:1999
Pour
R2A
ISO 11663:2014
Pour
R2A
ISO 13959:2014
Pour
R2A
ISO 23500:2014
Pour
R2A
PHE guidelines
Pour
TGEA
ISO 13959:2014
Pour
TGEA
PHE guidelines
Pour
TSA
European pharmacopoeia 5.0
Pour
YEA
European pharmacopoeia 5.0
Pour
YEA
ISO 11663:2014
Pour
YEA
ISO 13959:2014
Pour
YEA
ISO 6222:1999
Pour
YEA
Other; please state
Pour
YEA
PHE guidelines
Pour
YEA
UK Renal Association Guidelines
Spread
R2A
European pharmacopoeia 5.0
Spread
R2A
ISO 13959:2014
Spread
R2A
Other; please state
Spread
TGEA
European pharmacopoeia 5.0
Spread
TGEA
ISO 11663:2014
Spread
TSA
UK Renal Association Guidelines
The data in FEPTU reports is confidential
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1 1 2 2 1 1 1 3 2 2 2 1 1 1 1 1 1 3 1 1 4 1 2 1 1 1 1
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Performance Assessment Sheet Distribution
DW13
DW12
DW11
Sample
Total Viable Counts 17ºC 23ºC for 7 days score
DW13A DW13B DW12A DW12B DW11A DW11B
Total maximum possible score Total percentage
Performance Assessment Comment:
Overall Performance Assessment for Distributions DW13, DW12, DW11
Participants are reminded that to take advantage of the performance assessment overtime tool provided in the reports they need to take part in more than one distribution a year.
100
90-99
80-89
70-79
60-69
50-59
40-49
30-39
20-29
0
10-19
10
1-9
Your overall performance with the enumerations in the dialysis water proficiency testing samples for the current and previous two distributions is collated in the chart to the right.
20
0
Cumulative scores are calculated for the current and previous distribution for the Dialysis Water Scheme. Participants' cumulative scores for each of the examinations are compared with the maximum possible scores after every distribution.
30
Number of participants
Performance assessments are designed to alert participants to on -going problems with their examinations and are provided after every distribution. Scores are allocated to results reported for every parameter, for every sample to help assess performance.
40
Percentage achieved of max possible score for stipulated distributions
Performance Assessment Comment: Laboratories that achieve less than 70% of the maximum possible score are likely to be experiencing significant problems with their examinations and are advised to: a) refer to the relevant distribution reports for sample-specific comments b) refer to the website guidance documents: https://www.gov.uk/government/collections/external-quality-assessment-eqa-and-proficiency-testing-pt-for-food-water-and-environ mental-microbiology
c) contact the organisers for advice
The data in FEPTU reports is confidential
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The data in FEPTU reports is confidential
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The data in FEPTU reports is confidential
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