Standard Scheme 298 - Gov.uk
Summary of Results External Quality Assessment of Food Microbiology
Standard Scheme Distribution Number: 286
Sample Numbers: S0609, S0610
Distribution Date: Results Due: Report Date:
October 2016 11 November 2016 29 November 2016
Samples prepared and quality control tested by:
Angela Appea Thomas Harper Zak Prior Aneta Stranc Vincent Smith
Data analysed by:
Manchari Rajkumar Nita Patel
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
Page 1 of 21
Printed at 9:53 on Monday, 9 January, 2017
For further information on 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:
x = participants' result (expressed as a log 10 value) X = assigned value (participants' consensus median (expressed as a log 10 value))
Z = (x-X) σ
σ = the fixed standard deviation for the examination (calculated by FEPTU)
The σ-value expresses the acceptable difference between the individual participant 's result and the participants' consensus median. The σ-value used for calculating z-scores for all parameters in the Standard 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 are investigated to establish the possible cause. rule, PHE recommends that all questionable and unsatisfactory results are investigated.
As a general
FEPTU Quality control: To demonstrate homogeneity of the sample, a minimum of 10 freeze-dried vials, selected randomly from a batch, are tested in duplicate for parameters requiring enumeration and 10 freeze-dried vials are examined for pathogen detection.
To demonstrate stability of the sample, a minimum of nine vials, selected randomly from a batch, are examined throughout the distribution period, either for enumeration or pathogen detection. FEPTU results are determined using methods based on ISO methods and are included in the 'intended results' letters which provide guidance for participants regarding the assigned values. 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
All participants are reminded that reporting an incorrect or incomplete identification of pathogens from food samples could have serious public health implications. Similarly, the levels of micro-organisms reported in the sample may affect the subsequent outcome for the product. Participants are reminded that the purpose of scoring is to draw attention to incorrect or outlying results. Participants who report outlying results for enumerations on single occasions only should not be alarmed, although they should still assess the reason(s) for the outlying result. The results, as summarised in the performance assessment sheet included in this report, provide a more effective indication of on-going problems with food microbiology examinations.
The bar charts in this report are compiled using the processes outlined in the Guide to Scoring Systems and Statistics for the allocation of PHE scores. Z-scores are included on the sample-specific pages only; the relevant sections will be left blank if a z-score does not apply. Please contact FEPTU staff for advice and information: Repeat samples
Carmen Gomes or Kermin Daruwalla
Data Analysis
Nita Patel or Manchari Rajkumar
Microbiological advice
Nita Patel or Zak Prior
General comments and complaints
Nita Patel or Zak Prior
Scheme consultants
Melody Greenwood and Julie E. Russell
Scheme Co-ordinator
Nita Patel
Tel: Fax: Email:
+44 (0)20 8327 7119 +44 (0)20 8200 8264 [email protected]
Accreditation: PHE Food EQA Scheme for Standard is accredited by the United Kingdom Accreditation Service (UKAS) to ISO/IEC 17043:2010.
0006 The data in FEPTU reports is confidential
Page 2 of 21
Printed at 9:53 on Monday, 9 January, 2017
Sample: S0609 Listeria monocytogenes (4.2x10²) (wild strain), Cronobacter sakazakii (75) (wild strain), Clostridium
Contents:
perfringens (2.2x10⁴) (wild strain), Escherichia coli (2.0x10³) (wild strain), Aeromonas hydrophilia (2.4x10⁴) (wild strain) All levels are presented as colony forming units (cfu) per ml reconstituted sample
Expected Results: Examination
Expected Result
Listeria spp. (including L.mono)
Detected in 25g
L.monocytogenes
Detected in 25g
Cronobacter sakazakii
Detected in 25g
Clostridium perfringens
6.2x10³ - 6.2x10⁴ cfu g ⁻¹
Aerobic colony count
6.0x10³ - 6.0x10⁴ cfu g ⁻¹
Escherichia coli
1.0x10³ - 2.0x10⁴ cfu g ⁻¹
Your Result
Score
Z-score
Listeria spp. (including L.mono)
Total participants reporting for Listeria spp. (including L.mono)
108
Participants reporting correctly
106 (98%)
L.monocytogenes Total participants reporting for L.monocytogenes
124
Participants reporting correctly
124 (100%)
Cronobacter sakazakii Total participants reporting for Cronobacter sakazakii
36
Participants reporting correctly
32 (89%)
The data in FEPTU reports is confidential
Page 3 of 21
Printed at 9:53 on Monday, 9 January, 2017
Clostridium perfringens Total participants reporting for Clostridium perfringens
108
Total participants enumerating Clostridium perfringens
104
Participants reporting a high censored value
1
Assigned value (participants' median)
2.0x10⁴ cfu g⁻¹ (4.29 log₁₀)
Uncertainty of assigned value (Ux=log₁₀ cfu g⁻¹)
0.02
No. of outlying counts
8 (7 low / 1 high)
Participants mean
1.9x10⁴ cfu g⁻¹ (4.28 log₁₀)
Standard deviation of participants results *
0.19 log₁₀ cfu g⁻¹
FEPTU QC medians
▪
ISO 7937
2.2x10⁴ cfu g⁻¹ (4.34 log₁₀)
Aerobic colony count Total participants reporting for Aerobic colony count
135
Assigned value (participants' median)
1.9x10⁴ cfu g⁻¹ (4.28 log₁₀)
Uncertainty of assigned value (Ux=log₁₀ cfu g⁻¹)
0.02
No. of outlying counts
9 (5 low / 4 high)
Participants mean
1.9x10⁴ cfu g⁻¹ (4.28 log₁₀)
Standard deviation of participants results *
0.17 log₁₀ cfu g⁻¹
FEPTU QC median
2.6x10⁴ cfu g⁻¹ (4.41 log₁₀)
Escherichia coli Total participants reporting for Escherichia coli
136
Participants reporting a high censored value
1
Assigned value (participants' median)
6.4x10³ cfu g⁻¹ (3.81 log₁₀)
Uncertainty of assigned value (Ux=log₁₀ cfu g⁻¹)
0.06
No. of outlying counts
22 (13 low / 9 high)
Participants mean
5.4x10³ cfu g⁻¹ (3.73 log₁₀)
Standard deviation of participants results *
0.5 log₁₀ cfu g⁻¹
FEPTU QC median
2.0x10³ cfu g⁻¹ (3.3 log₁₀)
Total sent samples
149
Non-returns
2
Not examined
2
The fixed standard deviation value (σ value) used for calculation of the z-scores is 0.35 for all parameters. * Robust SD based on median absolute deviation about the participants' median (MAD).
The data in FEPTU reports is confidential
Page 4 of 21
Printed at 9:53 on Monday, 9 January, 2017
Clostridium perfringens reported by participants - Sample S0609 Outlying results 3.55-3.79
4.29 Participant Median (log 10 cfu g ) 4.34 FEPTU Median (log10 cfu g ) -1
-1
Outlying results
Outlying results
25
4.79
4.72-4.79
4.67-4.71
4.63-4.66
4.59-4.62
4.54-4.58
4.50-4.53
4.46-4.49
4.41-4.45
4.37-4.40
4.32-4.36
4.28-4.31
4.24-4.27
4.19-4.23
4.15-4.18
4.11-4.14
4.06-4.10
4.02-4.05
3.98-4.01
3.93-3.97
3.89-3.92
3.85-3.88
3.80-3.84
0
Log₁₀ cfu g⁻¹
Method based presentation S0609 : Clostridium perfringens
FEPTU Method: ISO 7937
Method
Number of Results
Excluded Results
Percentage of the total
Median
Robust SD
Range Reported
(Log₁₀ cfu g⁻¹)
(Log₁₀ cfu g⁻¹)
ISO 7937
73
0
70
4.28
0.17
2.56
-
4.72
Other
30
0
29
4.31
0.26
2.30
-
5.15
(Log₁₀ cfu g⁻¹)
Clostridium perfringens reported by participants - Sample S0609
3.80-3.84
-1
Outlying results
Outlying results
4.29 Participant Median (log 10 cfu g ) 4.34 FEPTU Median (log10 cfu g ) -1
3.55-3.79
20
15
10
5
>4.79
4.72-4.79
4.67-4.71
4.63-4.66
4.59-4.62
4.54-4.58
4.50-4.53
4.46-4.49
4.41-4.45
4.37-4.40
4.32-4.36
4.28-4.31
4.24-4.27
4.19-4.23
4.15-4.18
4.11-4.14
4.06-4.10
4.02-4.05
3.98-4.01
3.93-3.97
3.89-3.92
3.85-3.88
0 4.78
4.71-4.78
4.67-4.70
4.62-4.66
4.58-4.61
4.54-4.57
4.50-4.53
4.46-4.49
4.42-4.45
4.37-4.41
4.33-4.36
4.29-4.32
4.25-4.28
4.21-4.24
4.17-4.20
4.12-4.16
4.08-4.11
4.04-4.07
4.00-4.03
3.96-3.99
3.92-3.95
3.87-3.91
3.83-3.86
3.79-3.82
4.78
4.71-4.78
4.67-4.70
4.62-4.66
4.58-4.61
4.54-4.57
4.50-4.53
4.46-4.49
4.42-4.45
4.37-4.41
4.33-4.36
4.29-4.32
4.25-4.28
4.21-4.24
4.17-4.20
4.12-4.16
4.08-4.11
4.04-4.07
4.00-4.03
3.96-3.99
3.92-3.95
3.87-3.91
3.83-3.86
3.79-3.82
0 4.37
-1
Outlying results
Outlying results 2.65-3.00
3.81 Participant Median (log 10 cfu g ) 3.30 FEPTU Median (log10 cfu g ) -1
4.31-4.37
Outlying results
25
4.37
3.01-3.06
Outlying results
Outlying results 2.65-3.00
-1
4.31-4.37
Outlying results
20
3.81 Participant Median (log 10 cfu g ) 3.30 FEPTU Median (log10 cfu g ) -1
4.15
4.08-4.15
4.04-4.07
4.00-4.03
3.96-3.99
3.91-3.95
3.87-3.90
3.83-3.86
3.79-3.82
3.75-3.78
3.71-3.74
3.66-3.70
3.62-3.65
3.58-3.61
3.54-3.57
3.50-3.53
3.46-3.49
3.41-3.45
3.37-3.40
3.33-3.36
3.29-3.32
3.25-3.28
3.21-3.24
3.16-3.20
4.15
4.08-4.15
4.04-4.07
4.00-4.03
3.96-3.99
3.91-3.95
3.87-3.90
3.83-3.86
3.79-3.82
3.75-3.78
3.71-3.74
3.66-3.70
3.62-3.65
3.58-3.61
3.54-3.57
3.50-3.53
3.46-3.49
3.41-3.45
3.37-3.40
3.33-3.36
3.29-3.32
3.25-3.28
3.21-3.24
3.16-3.20
0
Standard Scheme Distribution Number: 286
Sample Numbers: S0609, S0610
Distribution Date: Results Due: Report Date:
October 2016 11 November 2016 29 November 2016
Samples prepared and quality control tested by:
Angela Appea Thomas Harper Zak Prior Aneta Stranc Vincent Smith
Data analysed by:
Manchari Rajkumar Nita Patel
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
Page 1 of 21
Printed at 9:53 on Monday, 9 January, 2017
For further information on 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:
x = participants' result (expressed as a log 10 value) X = assigned value (participants' consensus median (expressed as a log 10 value))
Z = (x-X) σ
σ = the fixed standard deviation for the examination (calculated by FEPTU)
The σ-value expresses the acceptable difference between the individual participant 's result and the participants' consensus median. The σ-value used for calculating z-scores for all parameters in the Standard 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 are investigated to establish the possible cause. rule, PHE recommends that all questionable and unsatisfactory results are investigated.
As a general
FEPTU Quality control: To demonstrate homogeneity of the sample, a minimum of 10 freeze-dried vials, selected randomly from a batch, are tested in duplicate for parameters requiring enumeration and 10 freeze-dried vials are examined for pathogen detection.
To demonstrate stability of the sample, a minimum of nine vials, selected randomly from a batch, are examined throughout the distribution period, either for enumeration or pathogen detection. FEPTU results are determined using methods based on ISO methods and are included in the 'intended results' letters which provide guidance for participants regarding the assigned values. 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
All participants are reminded that reporting an incorrect or incomplete identification of pathogens from food samples could have serious public health implications. Similarly, the levels of micro-organisms reported in the sample may affect the subsequent outcome for the product. Participants are reminded that the purpose of scoring is to draw attention to incorrect or outlying results. Participants who report outlying results for enumerations on single occasions only should not be alarmed, although they should still assess the reason(s) for the outlying result. The results, as summarised in the performance assessment sheet included in this report, provide a more effective indication of on-going problems with food microbiology examinations.
The bar charts in this report are compiled using the processes outlined in the Guide to Scoring Systems and Statistics for the allocation of PHE scores. Z-scores are included on the sample-specific pages only; the relevant sections will be left blank if a z-score does not apply. Please contact FEPTU staff for advice and information: Repeat samples
Carmen Gomes or Kermin Daruwalla
Data Analysis
Nita Patel or Manchari Rajkumar
Microbiological advice
Nita Patel or Zak Prior
General comments and complaints
Nita Patel or Zak Prior
Scheme consultants
Melody Greenwood and Julie E. Russell
Scheme Co-ordinator
Nita Patel
Tel: Fax: Email:
+44 (0)20 8327 7119 +44 (0)20 8200 8264 [email protected]
Accreditation: PHE Food EQA Scheme for Standard is accredited by the United Kingdom Accreditation Service (UKAS) to ISO/IEC 17043:2010.
0006 The data in FEPTU reports is confidential
Page 2 of 21
Printed at 9:53 on Monday, 9 January, 2017
Sample: S0609 Listeria monocytogenes (4.2x10²) (wild strain), Cronobacter sakazakii (75) (wild strain), Clostridium
Contents:
perfringens (2.2x10⁴) (wild strain), Escherichia coli (2.0x10³) (wild strain), Aeromonas hydrophilia (2.4x10⁴) (wild strain) All levels are presented as colony forming units (cfu) per ml reconstituted sample
Expected Results: Examination
Expected Result
Listeria spp. (including L.mono)
Detected in 25g
L.monocytogenes
Detected in 25g
Cronobacter sakazakii
Detected in 25g
Clostridium perfringens
6.2x10³ - 6.2x10⁴ cfu g ⁻¹
Aerobic colony count
6.0x10³ - 6.0x10⁴ cfu g ⁻¹
Escherichia coli
1.0x10³ - 2.0x10⁴ cfu g ⁻¹
Your Result
Score
Z-score
Listeria spp. (including L.mono)
Total participants reporting for Listeria spp. (including L.mono)
108
Participants reporting correctly
106 (98%)
L.monocytogenes Total participants reporting for L.monocytogenes
124
Participants reporting correctly
124 (100%)
Cronobacter sakazakii Total participants reporting for Cronobacter sakazakii
36
Participants reporting correctly
32 (89%)
The data in FEPTU reports is confidential
Page 3 of 21
Printed at 9:53 on Monday, 9 January, 2017
Clostridium perfringens Total participants reporting for Clostridium perfringens
108
Total participants enumerating Clostridium perfringens
104
Participants reporting a high censored value
1
Assigned value (participants' median)
2.0x10⁴ cfu g⁻¹ (4.29 log₁₀)
Uncertainty of assigned value (Ux=log₁₀ cfu g⁻¹)
0.02
No. of outlying counts
8 (7 low / 1 high)
Participants mean
1.9x10⁴ cfu g⁻¹ (4.28 log₁₀)
Standard deviation of participants results *
0.19 log₁₀ cfu g⁻¹
FEPTU QC medians
▪
ISO 7937
2.2x10⁴ cfu g⁻¹ (4.34 log₁₀)
Aerobic colony count Total participants reporting for Aerobic colony count
135
Assigned value (participants' median)
1.9x10⁴ cfu g⁻¹ (4.28 log₁₀)
Uncertainty of assigned value (Ux=log₁₀ cfu g⁻¹)
0.02
No. of outlying counts
9 (5 low / 4 high)
Participants mean
1.9x10⁴ cfu g⁻¹ (4.28 log₁₀)
Standard deviation of participants results *
0.17 log₁₀ cfu g⁻¹
FEPTU QC median
2.6x10⁴ cfu g⁻¹ (4.41 log₁₀)
Escherichia coli Total participants reporting for Escherichia coli
136
Participants reporting a high censored value
1
Assigned value (participants' median)
6.4x10³ cfu g⁻¹ (3.81 log₁₀)
Uncertainty of assigned value (Ux=log₁₀ cfu g⁻¹)
0.06
No. of outlying counts
22 (13 low / 9 high)
Participants mean
5.4x10³ cfu g⁻¹ (3.73 log₁₀)
Standard deviation of participants results *
0.5 log₁₀ cfu g⁻¹
FEPTU QC median
2.0x10³ cfu g⁻¹ (3.3 log₁₀)
Total sent samples
149
Non-returns
2
Not examined
2
The fixed standard deviation value (σ value) used for calculation of the z-scores is 0.35 for all parameters. * Robust SD based on median absolute deviation about the participants' median (MAD).
The data in FEPTU reports is confidential
Page 4 of 21
Printed at 9:53 on Monday, 9 January, 2017
Clostridium perfringens reported by participants - Sample S0609 Outlying results 3.55-3.79
4.29 Participant Median (log 10 cfu g ) 4.34 FEPTU Median (log10 cfu g ) -1
-1
Outlying results
Outlying results
25
4.79
4.72-4.79
4.67-4.71
4.63-4.66
4.59-4.62
4.54-4.58
4.50-4.53
4.46-4.49
4.41-4.45
4.37-4.40
4.32-4.36
4.28-4.31
4.24-4.27
4.19-4.23
4.15-4.18
4.11-4.14
4.06-4.10
4.02-4.05
3.98-4.01
3.93-3.97
3.89-3.92
3.85-3.88
3.80-3.84
0
Log₁₀ cfu g⁻¹
Method based presentation S0609 : Clostridium perfringens
FEPTU Method: ISO 7937
Method
Number of Results
Excluded Results
Percentage of the total
Median
Robust SD
Range Reported
(Log₁₀ cfu g⁻¹)
(Log₁₀ cfu g⁻¹)
ISO 7937
73
0
70
4.28
0.17
2.56
-
4.72
Other
30
0
29
4.31
0.26
2.30
-
5.15
(Log₁₀ cfu g⁻¹)
Clostridium perfringens reported by participants - Sample S0609
3.80-3.84
-1
Outlying results
Outlying results
4.29 Participant Median (log 10 cfu g ) 4.34 FEPTU Median (log10 cfu g ) -1
3.55-3.79
20
15
10
5
>4.79
4.72-4.79
4.67-4.71
4.63-4.66
4.59-4.62
4.54-4.58
4.50-4.53
4.46-4.49
4.41-4.45
4.37-4.40
4.32-4.36
4.28-4.31
4.24-4.27
4.19-4.23
4.15-4.18
4.11-4.14
4.06-4.10
4.02-4.05
3.98-4.01
3.93-3.97
3.89-3.92
3.85-3.88
0 4.78
4.71-4.78
4.67-4.70
4.62-4.66
4.58-4.61
4.54-4.57
4.50-4.53
4.46-4.49
4.42-4.45
4.37-4.41
4.33-4.36
4.29-4.32
4.25-4.28
4.21-4.24
4.17-4.20
4.12-4.16
4.08-4.11
4.04-4.07
4.00-4.03
3.96-3.99
3.92-3.95
3.87-3.91
3.83-3.86
3.79-3.82
4.78
4.71-4.78
4.67-4.70
4.62-4.66
4.58-4.61
4.54-4.57
4.50-4.53
4.46-4.49
4.42-4.45
4.37-4.41
4.33-4.36
4.29-4.32
4.25-4.28
4.21-4.24
4.17-4.20
4.12-4.16
4.08-4.11
4.04-4.07
4.00-4.03
3.96-3.99
3.92-3.95
3.87-3.91
3.83-3.86
3.79-3.82
0 4.37
-1
Outlying results
Outlying results 2.65-3.00
3.81 Participant Median (log 10 cfu g ) 3.30 FEPTU Median (log10 cfu g ) -1
4.31-4.37
Outlying results
25
4.37
3.01-3.06
Outlying results
Outlying results 2.65-3.00
-1
4.31-4.37
Outlying results
20
3.81 Participant Median (log 10 cfu g ) 3.30 FEPTU Median (log10 cfu g ) -1
4.15
4.08-4.15
4.04-4.07
4.00-4.03
3.96-3.99
3.91-3.95
3.87-3.90
3.83-3.86
3.79-3.82
3.75-3.78
3.71-3.74
3.66-3.70
3.62-3.65
3.58-3.61
3.54-3.57
3.50-3.53
3.46-3.49
3.41-3.45
3.37-3.40
3.33-3.36
3.29-3.32
3.25-3.28
3.21-3.24
3.16-3.20
4.15
4.08-4.15
4.04-4.07
4.00-4.03
3.96-3.99
3.91-3.95
3.87-3.90
3.83-3.86
3.79-3.82
3.75-3.78
3.71-3.74
3.66-3.70
3.62-3.65
3.58-3.61
3.54-3.57
3.50-3.53
3.46-3.49
3.41-3.45
3.37-3.40
3.33-3.36
3.29-3.32
3.25-3.28
3.21-3.24
3.16-3.20
0
