Standard Scheme - Gov.uk
Summary of Results External Quality Assessment of Food Microbiology
Standard Scheme Distribution Number: 290
Sample Numbers: S0617, S0618
Distribution Date: Results Due: Report Date:
February 2017 31 March 2017 18 April 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:
Manchari Rajkumar Nita Patel
Report compiled by:
Joanna Donn Manchari Rajkumar
Authorised by:
Nita Patel (Ref: FNC587) AMENDED REPORT incorrect results shown
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 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:
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 σpt-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]
FEPTU's website
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
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Sample: S0617 Contents:
Bacillus cereus 1.1x10⁴ (wild strain), Staphylococcus aureus 4.6x10³ (wild strain), Listeria monocytogenes 2.9x10³ (wild strain), Enterobacter cloacae 5.4x10² (wild strain), Staphylococcus sciuri 6.6x10² (wild strain)
All levels are presented as colony forming units (cfu) per ml reconstituted sample All levels are presented as colony forming units (cfu) per ml reconstituted sample
Expected Results: Examination
Expected Result
Presumptive B.cereus
2.2x10³ - 2.2x10⁴ cfu g ⁻¹
Coagulase-positive staphylococci
1.6x10³ - 1.6x10⁴ cfu g ⁻¹
Listeria spp. (including L.mono)
7.3x10² - 7.3x10³ cfu g ⁻¹
L.monocytogenes
6.7x10² - 6.7x10³ cfu g ⁻¹
Aerobic colony count
3.8x10³ - 3.8x10⁴ cfu g ⁻¹
Coliform
1.7x10² - 1.7x10³ cfu g ⁻¹
Your Result
Score
Z-score
Presumptive B.cereus
Total participants reporting for Presumptive B.cereus
99
Total participants enumerating Presumptive B.cereus
98
Assigned value (participants' median)
6.8x10³ cfu g⁻¹ (3.83 log₁₀)
Uncertainty of assigned value (U(Xpt)=log₁₀ cfu g⁻¹)
0.03
No. of outlying counts
9 (7 low / 2 high)
Participants mean
6.5x10³ cfu g⁻¹ (3.81 log₁₀)
Standard deviation of participants results *
0.21 log₁₀ cfu g⁻¹
FEPTU QC medians
▪
ISO 7932
1.1x10⁴ cfu g⁻¹ (4.04 log₁₀)
Coagulase-positive staphylococci Total participants reporting for Coagulase-positive staphylococci
122
Total participants enumerating Coagulase-positive staphylococci
119
Participants reporting a low censored value
1
Assigned value (participants' median)
5.0x10³ cfu g⁻¹ (3.7 log₁₀)
Uncertainty of assigned value (U(Xpt)=log₁₀ cfu g⁻¹)
0.02
No. of outlying counts
9 (8 low / 1 high)
Participants mean
5.0x10³ cfu g⁻¹ (3.7 log₁₀)
Standard deviation of participants results *
0.15 log₁₀ cfu g⁻¹
FEPTU QC medians
▪
ISO 6888-1
The data in FEPTU reports is confidential
4.6x10³ cfu g⁻¹ (3.66 log₁₀)
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Listeria spp. (including L.mono) Total participants reporting for Listeria spp. (including L.mono)
93
Total participants enumerating Listeria spp. (including L.mono)
82
Assigned value (participants' median)
2.3x10³ cfu g⁻¹ (3.36 log₁₀)
Uncertainty of assigned value (U(Xpt)=log₁₀ cfu g⁻¹)
0.02
No. of outlying counts
8 (5 low / 3 high)
Participants mean
2.3x10³ cfu g⁻¹ (3.36 log₁₀)
Standard deviation of participants results *
0.16 log₁₀ cfu g⁻¹
FEPTU QC medians
▪
ISO 11290-2
2.9x10³ cfu g⁻¹ (3.46 log₁₀)
L.monocytogenes Total participants reporting for L.monocytogenes
115
Total participants enumerating L.monocytogenes
102
Assigned value (participants' median)
2.1x10³ cfu g⁻¹ (3.33 log₁₀)
Uncertainty of assigned value (U(Xpt)=log₁₀ cfu g⁻¹)
0.02
No. of outlying counts
10 (6 low / 4 high)
Participants mean
2.1x10³ cfu g⁻¹ (3.33 log₁₀)
Standard deviation of participants results *
0.15 log₁₀ cfu g⁻¹
FEPTU QC medians
▪
ISO 11290-2
2.9x10³ cfu g⁻¹ (3.46 log₁₀)
Aerobic colony count Total participants reporting for Aerobic colony count
126
Assigned value (participants' median)
1.2x10⁴ cfu g⁻¹ (4.08 log₁₀)
Uncertainty of assigned value (U(Xpt)=log₁₀ cfu g⁻¹)
0.02
No. of outlying counts
6 (3 low / 3 high)
Participants mean
1.3x10⁴ cfu g⁻¹ (4.1 log₁₀)
Standard deviation of participants results *
0.16 log₁₀ cfu g⁻¹
FEPTU QC median
1.2x10⁴ cfu g⁻¹ (4.08 log₁₀)
Coliform Total participants reporting for Coliform
93
Assigned value (participants' median)
5.5x10² cfu g⁻¹ (2.74 log₁₀)
Uncertainty of assigned value (U(Xpt)=log₁₀ cfu g⁻¹)
0.05
No. of outlying counts
13 (9 low / 4 high)
Participants mean
5.3x10² cfu g⁻¹ (2.73 log₁₀)
Standard deviation of participants results *
0.35 log₁₀ cfu g⁻¹
FEPTU QC median
5.4x10² cfu g⁻¹ (2.73 log₁₀)
Total sent samples
140
Non-returns
3
Not examined
5
The fixed standard deviation value (σpt value) used for calculation of the z-scores is 0.35 for all parameters. * Robust S* based on median absolute deviation about the participants' median (MADe).
The data in FEPTU reports is confidential
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Sample: S0618 Contents:
Bacillus cereus 5.8x10³ (wild strain), Staphylococcus aureus 6.8x10⁴ (wild strain), Listeria monocytogenes 6.6x10³ (wild strain), Listeria innocua 1.1x10³ (wild strain), Enterobacter cloacae 7.9x10³ (wild strain), Bacillus licheniformis 4.0x10² (wild strain)
All levels are presented as colony forming units (cfu) per ml reconstituted sample All levels are presented as colony forming units (cfu) per ml reconstituted sample
Expected Results: Examination
Expected Result
Presumptive B.cereus
1.6x10³ - 1.6x10⁴ cfu g ⁻¹
Coagulase-positive staphylococci
2.0x10⁴ - 2.0x10⁵ cfu g ⁻¹
Listeria spp. (including L.mono)
2.1x10³ - 2.1x10⁴ cfu g ⁻¹
L.monocytogenes
1.7x10³ - 1.7x10⁴ cfu g ⁻¹
Aerobic colony count
2.7x10⁴ - 2.7x10⁵ cfu g ⁻¹
Coliform
2.1x10³ - 2.1x10⁴ cfu g ⁻¹
Examination
Your Result
Result 2
Score
Z-score
Z-score
Presumptive B.cereus
Total participants reporting for Presumptive B.cereus
95
Total participants enumerating Presumptive B.cereus
94
Participants reporting a low censored value
2
Assigned value (participants' median)
5.0x10³ cfu g⁻¹ (3.7 log₁₀)
Uncertainty of assigned value (U(Xpt)=log₁₀ cfu g⁻¹)
0.02
No. of outlying counts
7 (6 low / 1 high)
Participants mean
4.8x10³ cfu g⁻¹ (3.68 log₁₀)
Standard deviation of participants results *
0.16 log₁₀ cfu g⁻¹
FEPTU QC medians
▪
ISO 7932
5.8x10³ cfu g⁻¹ (3.76 log₁₀)
Coagulase-positive staphylococci Total participants reporting for Coagulase-positive staphylococci
120
Total participants enumerating Coagulase-positive staphylococci
118
Participants reporting a low censored value
2
Participants reporting a high censored value
1
Assigned value (participants' median)
6.3x10⁴ cfu g⁻¹ (4.8 log₁₀)
Uncertainty of assigned value (U(Xpt)=log₁₀ cfu g⁻¹)
0.02
No. of outlying counts
11 (9 low / 2 high)
Participants mean
6.3x10⁴ cfu g⁻¹ (4.8 log₁₀)
Standard deviation of participants results *
0.16 log₁₀ cfu g⁻¹
FEPTU QC medians
▪
ISO 6888-1
The data in FEPTU reports is confidential
6.8x10⁴ cfu g⁻¹ (4.83 log₁₀)
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Listeria spp. (including L.mono) Total participants reporting for Listeria spp. (including L.mono)
91
Total participants enumerating Listeria spp. (including L.mono)
80
Assigned value (participants' median)
6.7x10³ cfu g⁻¹ (3.83 log₁₀)
Uncertainty of assigned value (U(Xpt)=log₁₀ cfu g⁻¹)
0.04
No. of outlying counts
8 (5 low / 3 high)
Participants mean
6.3x10³ cfu g⁻¹ (3.8 log₁₀)
Standard deviation of participants results *
0.25 log₁₀ cfu g⁻¹
FEPTU QC medians
▪
ISO 11290-2
7.7x10³ cfu g⁻¹ (3.89 log₁₀)
L.monocytogenes Total participants reporting for L.monocytogenes
113
Total participants enumerating L.monocytogenes
100
Participants reporting a low censored value
1
Assigned value (participants' median)
5.4x10³ cfu g⁻¹ (3.73 log₁₀)
Uncertainty of assigned value (U(Xpt)=log₁₀ cfu g⁻¹)
0.03
No. of outlying counts
12 (8 low / 4 high)
Participants mean
5.3x10³ cfu g⁻¹ (3.72 log₁₀)
Standard deviation of participants results *
0.24 log₁₀ cfu g⁻¹
FEPTU QC medians
▪
ISO 11290-2
6.6x10³ cfu g⁻¹ (3.82 log₁₀)
Aerobic colony count Total participants reporting for Aerobic colony count
124
Assigned value (participants' median)
8.4x10⁴ cfu g⁻¹ (4.92 log₁₀)
Uncertainty of assigned value (U(Xpt)=log₁₀ cfu g⁻¹)
0.01
No. of outlying counts
7 (5 low / 2 high)
Participants mean
8.3x10⁴ cfu g⁻¹ (4.92 log₁₀)
Standard deviation of participants results *
0.11 log₁₀ cfu g⁻¹
FEPTU QC median
5.9x10⁴ cfu g⁻¹ (4.77 log₁₀)
Coliform Total participants reporting for Coliform
90
Assigned value (participants' median)
6.7x10³ cfu g⁻¹ (3.83 log₁₀)
Uncertainty of assigned value (U(Xpt)=log₁₀ cfu g⁻¹)
0.04
No. of outlying counts
14 (9 low / 5 high)
Participants mean
6.2x10³ cfu g⁻¹ (3.8 log₁₀)
Standard deviation of participants results *
0.32 log₁₀ cfu g⁻¹
FEPTU QC median
7.9x10³ cfu g⁻¹ (3.9 log₁₀)
Total sent samples
140
Non-returns
3
Not examined
6
The fixed standard deviation value (σpt value) used for calculation of the z-scores is 0.35 for all parameters. * Robust S* based on median absolute deviation about the participants' median (MADe).
The data in FEPTU reports is confidential
Page 6 of 30
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Presumptive B.cereus reported by participants - Sample S0617 Outlying results 3.17-3.33
3.83 Participant Median (log 10 cfu g ) 4.04 FEPTU Median (log10 cfu g ) -1
-1
Outlying results
Outlying results
25
4.33
4.26-4.33
4.21-4.25
4.17-4.20
4.13-4.16
4.08-4.12
4.04-4.07
4.00-4.03
3.95-3.99
3.91-3.94
3.87-3.90
3.82-3.86
3.78-3.81
3.74-3.77
3.69-3.73
3.65-3.68
3.60-3.64
3.56-3.59
3.52-3.55
3.47-3.51
3.43-3.46
3.39-3.42
3.34-3.38
0
Log₁₀ cfu g⁻¹
Method based presentation S0617 : Presumptive B.cereus
FEPTU Method: ISO 7932
Method
Number of Results
Excluded Results
Percentage of the total
Median
Robust S*
(Log₁₀ cfu g⁻¹)
(Log₁₀ cfu g⁻¹)
ISO 7932
73
0
74
3.86
0.21
0.00
-
5.00
Other
25
0
25
3.72
0.22
2.53
-
4.08
Range Reported (Log₁₀ cfu g⁻¹)
Presumptive B.cereus reported by participants - Sample S0617
3.34-3.38
Outlying results
Outlying results
3.83 Participant Median (log 10 cfu g ) 4.04 FEPTU Median (log10 cfu g ) -1
3.17-3.33
20
-1
15
10
5
>4.33
4.26-4.33
4.21-4.25
4.17-4.20
4.13-4.16
4.08-4.12
4.04-4.07
4.00-4.03
3.95-3.99
3.91-3.94
3.87-3.90
3.82-3.86
3.78-3.81
3.74-3.77
3.69-3.73
3.65-3.68
3.60-3.64
3.56-3.59
3.52-3.55
3.47-3.51
3.43-3.46
3.39-3.42
0 4.20
4.12-4.20
4.08-4.11
4.04-4.07
3.99-4.03
3.95-3.98
3.91-3.94
3.86-3.90
3.82-3.85
3.78-3.81
3.73-3.77
3.69-3.72
3.64-3.68
3.60-3.63
3.56-3.59
3.51-3.55
3.47-3.50
3.43-3.46
3.38-3.42
3.34-3.37
3.30-3.33
3.25-3.29
0 3.86
3.79-3.86
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
3.12-3.15
3.08-3.11
3.04-3.07
3.00-3.03
2.96-2.99
2.92-2.95
2.87-2.91
3.86
3.79-3.86
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
3.12-3.15
3.08-3.11
3.04-3.07
3.00-3.03
2.96-2.99
2.92-2.95
2.87-2.91
0 3.83
3.75-3.83
3.71-3.74
3.66-3.70
3.62-3.65
3.58-3.61
3.53-3.57
3.49-3.52
3.45-3.48
3.40-3.44
3.36-3.39
3.32-3.35
3.27-3.31
3.23-3.26
3.19-3.22
3.14-3.18
3.10-3.13
3.06-3.09
3.01-3.05
2.97-3.00
2.93-2.96
2.88-2.92
0 4.58
4.51-4.58
4.46-4.50
4.42-4.45
4.38-4.41
4.34-4.37
4.30-4.33
4.26-4.29
4.21-4.25
4.17-4.20
4.13-4.16
4.09-4.12
4.05-4.08
4.01-4.04
3.97-4.00
3.92-3.96
3.88-3.91
3.84-3.87
3.80-3.83
3.76-3.79
3.72-3.75
3.67-3.71
3.63-3.66
3.59-3.62
4.58
4.51-4.58
4.46-4.50
4.42-4.45
4.38-4.41
4.34-4.37
4.30-4.33
4.26-4.29
4.21-4.25
4.17-4.20
4.13-4.16
4.09-4.12
4.05-4.08
4.01-4.04
3.97-4.00
3.92-3.96
3.88-3.91
3.84-3.87
3.80-3.83
3.76-3.79
3.72-3.75
3.67-3.71
3.63-3.66
3.59-3.62
0 3.24
3.16-3.24
3.12-3.15
3.07-3.11
3.03-3.06
2.98-3.02
2.94-2.97
2.90-2.93
2.85-2.89
2.81-2.84
2.77-2.80
2.72-2.76
2.68-2.71
2.64-2.67
2.59-2.63
2.55-2.58
2.50-2.54
2.46-2.49
2.42-2.45
2.37-2.41
2.33-2.36
2.29-2.32
0 4.20
4.12-4.20
4.08-4.11
4.04-4.07
3.99-4.03
3.95-3.98
3.91-3.94
3.86-3.90
3.82-3.85
3.78-3.81
3.73-3.77
3.69-3.72
3.64-3.68
3.60-3.63
3.56-3.59
3.51-3.55
3.47-3.50
3.43-3.46
3.38-3.42
3.34-3.37
3.30-3.33
3.25-3.29
0 5.30
5.22-5.30
5.18-5.21
5.14-5.17
5.09-5.13
5.05-5.08
5.01-5.04
4.96-5.00
4.92-4.95
4.88-4.91
4.83-4.87
4.79-4.82
4.75-4.78
4.70-4.74
4.66-4.69
4.62-4.65
4.57-4.61
4.53-4.56
4.48-4.52
4.44-4.47
4.40-4.43
4.35-4.39
0 4.33
4.25-4.33
4.21-4.24
4.16-4.20
4.12-4.15
4.08-4.11
4.03-4.07
3.99-4.02
3.95-3.98
3.90-3.94
3.86-3.89
3.82-3.85
3.77-3.81
3.73-3.76
3.69-3.72
3.64-3.68
3.60-3.63
3.56-3.59
3.51-3.55
3.47-3.50
3.43-3.46
3.38-3.42
0 4.23
4.16-4.23
4.11-4.15
4.07-4.10
4.03-4.06
3.98-4.02
3.94-3.97
3.90-3.93
3.85-3.89
3.81-3.84
3.77-3.80
3.72-3.76
3.68-3.71
3.63-3.67
3.59-3.62
3.55-3.58
3.50-3.54
3.46-3.49
3.42-3.45
3.37-3.41
3.33-3.36
3.29-3.32
0 5.42
5.35-5.42
5.31-5.34
5.27-5.30
5.23-5.26
5.18-5.22
5.14-5.17
5.10-5.13
5.06-5.09
5.02-5.05
4.98-5.01
4.94-4.97
4.89-4.93
4.85-4.88
4.81-4.84
4.77-4.80
4.73-4.76
4.69-4.72
4.64-4.68
4.60-4.63
4.56-4.59
4.52-4.55
4.48-4.51
4.43-4.47
5.42
5.35-5.42
5.31-5.34
5.27-5.30
5.23-5.26
5.18-5.22
5.14-5.17
5.10-5.13
5.06-5.09
5.02-5.05
4.98-5.01
4.94-4.97
4.89-4.93
4.85-4.88
4.81-4.84
4.77-4.80
4.73-4.76
4.69-4.72
4.64-4.68
4.60-4.63
4.56-4.59
4.52-4.55
4.48-4.51
4.43-4.47
0 4.33
4.25-4.33
4.20-4.24
4.16-4.19
4.12-4.15
4.07-4.11
4.03-4.06
3.99-4.02
3.94-3.98
3.90-3.93
3.85-3.89
3.81-3.84
3.77-3.80
3.72-3.76
3.68-3.71
3.64-3.67
3.59-3.63
3.55-3.58
3.51-3.54
3.46-3.50
3.42-3.45
3.37-3.41
0
Standard Scheme Distribution Number: 290
Sample Numbers: S0617, S0618
Distribution Date: Results Due: Report Date:
February 2017 31 March 2017 18 April 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:
Manchari Rajkumar Nita Patel
Report compiled by:
Joanna Donn Manchari Rajkumar
Authorised by:
Nita Patel (Ref: FNC587) AMENDED REPORT incorrect results shown
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 30
Printed at 7:50 on Thursday, 20 April, 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:
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 σpt-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]
FEPTU's website
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 30
Printed at 7:50 on Thursday, 20 April, 2017
Sample: S0617 Contents:
Bacillus cereus 1.1x10⁴ (wild strain), Staphylococcus aureus 4.6x10³ (wild strain), Listeria monocytogenes 2.9x10³ (wild strain), Enterobacter cloacae 5.4x10² (wild strain), Staphylococcus sciuri 6.6x10² (wild strain)
All levels are presented as colony forming units (cfu) per ml reconstituted sample All levels are presented as colony forming units (cfu) per ml reconstituted sample
Expected Results: Examination
Expected Result
Presumptive B.cereus
2.2x10³ - 2.2x10⁴ cfu g ⁻¹
Coagulase-positive staphylococci
1.6x10³ - 1.6x10⁴ cfu g ⁻¹
Listeria spp. (including L.mono)
7.3x10² - 7.3x10³ cfu g ⁻¹
L.monocytogenes
6.7x10² - 6.7x10³ cfu g ⁻¹
Aerobic colony count
3.8x10³ - 3.8x10⁴ cfu g ⁻¹
Coliform
1.7x10² - 1.7x10³ cfu g ⁻¹
Your Result
Score
Z-score
Presumptive B.cereus
Total participants reporting for Presumptive B.cereus
99
Total participants enumerating Presumptive B.cereus
98
Assigned value (participants' median)
6.8x10³ cfu g⁻¹ (3.83 log₁₀)
Uncertainty of assigned value (U(Xpt)=log₁₀ cfu g⁻¹)
0.03
No. of outlying counts
9 (7 low / 2 high)
Participants mean
6.5x10³ cfu g⁻¹ (3.81 log₁₀)
Standard deviation of participants results *
0.21 log₁₀ cfu g⁻¹
FEPTU QC medians
▪
ISO 7932
1.1x10⁴ cfu g⁻¹ (4.04 log₁₀)
Coagulase-positive staphylococci Total participants reporting for Coagulase-positive staphylococci
122
Total participants enumerating Coagulase-positive staphylococci
119
Participants reporting a low censored value
1
Assigned value (participants' median)
5.0x10³ cfu g⁻¹ (3.7 log₁₀)
Uncertainty of assigned value (U(Xpt)=log₁₀ cfu g⁻¹)
0.02
No. of outlying counts
9 (8 low / 1 high)
Participants mean
5.0x10³ cfu g⁻¹ (3.7 log₁₀)
Standard deviation of participants results *
0.15 log₁₀ cfu g⁻¹
FEPTU QC medians
▪
ISO 6888-1
The data in FEPTU reports is confidential
4.6x10³ cfu g⁻¹ (3.66 log₁₀)
Page 3 of 30
Printed at 7:50 on Thursday, 20 April, 2017
Listeria spp. (including L.mono) Total participants reporting for Listeria spp. (including L.mono)
93
Total participants enumerating Listeria spp. (including L.mono)
82
Assigned value (participants' median)
2.3x10³ cfu g⁻¹ (3.36 log₁₀)
Uncertainty of assigned value (U(Xpt)=log₁₀ cfu g⁻¹)
0.02
No. of outlying counts
8 (5 low / 3 high)
Participants mean
2.3x10³ cfu g⁻¹ (3.36 log₁₀)
Standard deviation of participants results *
0.16 log₁₀ cfu g⁻¹
FEPTU QC medians
▪
ISO 11290-2
2.9x10³ cfu g⁻¹ (3.46 log₁₀)
L.monocytogenes Total participants reporting for L.monocytogenes
115
Total participants enumerating L.monocytogenes
102
Assigned value (participants' median)
2.1x10³ cfu g⁻¹ (3.33 log₁₀)
Uncertainty of assigned value (U(Xpt)=log₁₀ cfu g⁻¹)
0.02
No. of outlying counts
10 (6 low / 4 high)
Participants mean
2.1x10³ cfu g⁻¹ (3.33 log₁₀)
Standard deviation of participants results *
0.15 log₁₀ cfu g⁻¹
FEPTU QC medians
▪
ISO 11290-2
2.9x10³ cfu g⁻¹ (3.46 log₁₀)
Aerobic colony count Total participants reporting for Aerobic colony count
126
Assigned value (participants' median)
1.2x10⁴ cfu g⁻¹ (4.08 log₁₀)
Uncertainty of assigned value (U(Xpt)=log₁₀ cfu g⁻¹)
0.02
No. of outlying counts
6 (3 low / 3 high)
Participants mean
1.3x10⁴ cfu g⁻¹ (4.1 log₁₀)
Standard deviation of participants results *
0.16 log₁₀ cfu g⁻¹
FEPTU QC median
1.2x10⁴ cfu g⁻¹ (4.08 log₁₀)
Coliform Total participants reporting for Coliform
93
Assigned value (participants' median)
5.5x10² cfu g⁻¹ (2.74 log₁₀)
Uncertainty of assigned value (U(Xpt)=log₁₀ cfu g⁻¹)
0.05
No. of outlying counts
13 (9 low / 4 high)
Participants mean
5.3x10² cfu g⁻¹ (2.73 log₁₀)
Standard deviation of participants results *
0.35 log₁₀ cfu g⁻¹
FEPTU QC median
5.4x10² cfu g⁻¹ (2.73 log₁₀)
Total sent samples
140
Non-returns
3
Not examined
5
The fixed standard deviation value (σpt value) used for calculation of the z-scores is 0.35 for all parameters. * Robust S* based on median absolute deviation about the participants' median (MADe).
The data in FEPTU reports is confidential
Page 4 of 30
Printed at 7:50 on Thursday, 20 April, 2017
Sample: S0618 Contents:
Bacillus cereus 5.8x10³ (wild strain), Staphylococcus aureus 6.8x10⁴ (wild strain), Listeria monocytogenes 6.6x10³ (wild strain), Listeria innocua 1.1x10³ (wild strain), Enterobacter cloacae 7.9x10³ (wild strain), Bacillus licheniformis 4.0x10² (wild strain)
All levels are presented as colony forming units (cfu) per ml reconstituted sample All levels are presented as colony forming units (cfu) per ml reconstituted sample
Expected Results: Examination
Expected Result
Presumptive B.cereus
1.6x10³ - 1.6x10⁴ cfu g ⁻¹
Coagulase-positive staphylococci
2.0x10⁴ - 2.0x10⁵ cfu g ⁻¹
Listeria spp. (including L.mono)
2.1x10³ - 2.1x10⁴ cfu g ⁻¹
L.monocytogenes
1.7x10³ - 1.7x10⁴ cfu g ⁻¹
Aerobic colony count
2.7x10⁴ - 2.7x10⁵ cfu g ⁻¹
Coliform
2.1x10³ - 2.1x10⁴ cfu g ⁻¹
Examination
Your Result
Result 2
Score
Z-score
Z-score
Presumptive B.cereus
Total participants reporting for Presumptive B.cereus
95
Total participants enumerating Presumptive B.cereus
94
Participants reporting a low censored value
2
Assigned value (participants' median)
5.0x10³ cfu g⁻¹ (3.7 log₁₀)
Uncertainty of assigned value (U(Xpt)=log₁₀ cfu g⁻¹)
0.02
No. of outlying counts
7 (6 low / 1 high)
Participants mean
4.8x10³ cfu g⁻¹ (3.68 log₁₀)
Standard deviation of participants results *
0.16 log₁₀ cfu g⁻¹
FEPTU QC medians
▪
ISO 7932
5.8x10³ cfu g⁻¹ (3.76 log₁₀)
Coagulase-positive staphylococci Total participants reporting for Coagulase-positive staphylococci
120
Total participants enumerating Coagulase-positive staphylococci
118
Participants reporting a low censored value
2
Participants reporting a high censored value
1
Assigned value (participants' median)
6.3x10⁴ cfu g⁻¹ (4.8 log₁₀)
Uncertainty of assigned value (U(Xpt)=log₁₀ cfu g⁻¹)
0.02
No. of outlying counts
11 (9 low / 2 high)
Participants mean
6.3x10⁴ cfu g⁻¹ (4.8 log₁₀)
Standard deviation of participants results *
0.16 log₁₀ cfu g⁻¹
FEPTU QC medians
▪
ISO 6888-1
The data in FEPTU reports is confidential
6.8x10⁴ cfu g⁻¹ (4.83 log₁₀)
Page 5 of 30
Printed at 7:50 on Thursday, 20 April, 2017
Listeria spp. (including L.mono) Total participants reporting for Listeria spp. (including L.mono)
91
Total participants enumerating Listeria spp. (including L.mono)
80
Assigned value (participants' median)
6.7x10³ cfu g⁻¹ (3.83 log₁₀)
Uncertainty of assigned value (U(Xpt)=log₁₀ cfu g⁻¹)
0.04
No. of outlying counts
8 (5 low / 3 high)
Participants mean
6.3x10³ cfu g⁻¹ (3.8 log₁₀)
Standard deviation of participants results *
0.25 log₁₀ cfu g⁻¹
FEPTU QC medians
▪
ISO 11290-2
7.7x10³ cfu g⁻¹ (3.89 log₁₀)
L.monocytogenes Total participants reporting for L.monocytogenes
113
Total participants enumerating L.monocytogenes
100
Participants reporting a low censored value
1
Assigned value (participants' median)
5.4x10³ cfu g⁻¹ (3.73 log₁₀)
Uncertainty of assigned value (U(Xpt)=log₁₀ cfu g⁻¹)
0.03
No. of outlying counts
12 (8 low / 4 high)
Participants mean
5.3x10³ cfu g⁻¹ (3.72 log₁₀)
Standard deviation of participants results *
0.24 log₁₀ cfu g⁻¹
FEPTU QC medians
▪
ISO 11290-2
6.6x10³ cfu g⁻¹ (3.82 log₁₀)
Aerobic colony count Total participants reporting for Aerobic colony count
124
Assigned value (participants' median)
8.4x10⁴ cfu g⁻¹ (4.92 log₁₀)
Uncertainty of assigned value (U(Xpt)=log₁₀ cfu g⁻¹)
0.01
No. of outlying counts
7 (5 low / 2 high)
Participants mean
8.3x10⁴ cfu g⁻¹ (4.92 log₁₀)
Standard deviation of participants results *
0.11 log₁₀ cfu g⁻¹
FEPTU QC median
5.9x10⁴ cfu g⁻¹ (4.77 log₁₀)
Coliform Total participants reporting for Coliform
90
Assigned value (participants' median)
6.7x10³ cfu g⁻¹ (3.83 log₁₀)
Uncertainty of assigned value (U(Xpt)=log₁₀ cfu g⁻¹)
0.04
No. of outlying counts
14 (9 low / 5 high)
Participants mean
6.2x10³ cfu g⁻¹ (3.8 log₁₀)
Standard deviation of participants results *
0.32 log₁₀ cfu g⁻¹
FEPTU QC median
7.9x10³ cfu g⁻¹ (3.9 log₁₀)
Total sent samples
140
Non-returns
3
Not examined
6
The fixed standard deviation value (σpt value) used for calculation of the z-scores is 0.35 for all parameters. * Robust S* based on median absolute deviation about the participants' median (MADe).
The data in FEPTU reports is confidential
Page 6 of 30
Printed at 7:50 on Thursday, 20 April, 2017
Presumptive B.cereus reported by participants - Sample S0617 Outlying results 3.17-3.33
3.83 Participant Median (log 10 cfu g ) 4.04 FEPTU Median (log10 cfu g ) -1
-1
Outlying results
Outlying results
25
4.33
4.26-4.33
4.21-4.25
4.17-4.20
4.13-4.16
4.08-4.12
4.04-4.07
4.00-4.03
3.95-3.99
3.91-3.94
3.87-3.90
3.82-3.86
3.78-3.81
3.74-3.77
3.69-3.73
3.65-3.68
3.60-3.64
3.56-3.59
3.52-3.55
3.47-3.51
3.43-3.46
3.39-3.42
3.34-3.38
0
Log₁₀ cfu g⁻¹
Method based presentation S0617 : Presumptive B.cereus
FEPTU Method: ISO 7932
Method
Number of Results
Excluded Results
Percentage of the total
Median
Robust S*
(Log₁₀ cfu g⁻¹)
(Log₁₀ cfu g⁻¹)
ISO 7932
73
0
74
3.86
0.21
0.00
-
5.00
Other
25
0
25
3.72
0.22
2.53
-
4.08
Range Reported (Log₁₀ cfu g⁻¹)
Presumptive B.cereus reported by participants - Sample S0617
3.34-3.38
Outlying results
Outlying results
3.83 Participant Median (log 10 cfu g ) 4.04 FEPTU Median (log10 cfu g ) -1
3.17-3.33
20
-1
15
10
5
>4.33
4.26-4.33
4.21-4.25
4.17-4.20
4.13-4.16
4.08-4.12
4.04-4.07
4.00-4.03
3.95-3.99
3.91-3.94
3.87-3.90
3.82-3.86
3.78-3.81
3.74-3.77
3.69-3.73
3.65-3.68
3.60-3.64
3.56-3.59
3.52-3.55
3.47-3.51
3.43-3.46
3.39-3.42
0 4.20
4.12-4.20
4.08-4.11
4.04-4.07
3.99-4.03
3.95-3.98
3.91-3.94
3.86-3.90
3.82-3.85
3.78-3.81
3.73-3.77
3.69-3.72
3.64-3.68
3.60-3.63
3.56-3.59
3.51-3.55
3.47-3.50
3.43-3.46
3.38-3.42
3.34-3.37
3.30-3.33
3.25-3.29
0 3.86
3.79-3.86
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
3.12-3.15
3.08-3.11
3.04-3.07
3.00-3.03
2.96-2.99
2.92-2.95
2.87-2.91
3.86
3.79-3.86
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
3.12-3.15
3.08-3.11
3.04-3.07
3.00-3.03
2.96-2.99
2.92-2.95
2.87-2.91
0 3.83
3.75-3.83
3.71-3.74
3.66-3.70
3.62-3.65
3.58-3.61
3.53-3.57
3.49-3.52
3.45-3.48
3.40-3.44
3.36-3.39
3.32-3.35
3.27-3.31
3.23-3.26
3.19-3.22
3.14-3.18
3.10-3.13
3.06-3.09
3.01-3.05
2.97-3.00
2.93-2.96
2.88-2.92
0 4.58
4.51-4.58
4.46-4.50
4.42-4.45
4.38-4.41
4.34-4.37
4.30-4.33
4.26-4.29
4.21-4.25
4.17-4.20
4.13-4.16
4.09-4.12
4.05-4.08
4.01-4.04
3.97-4.00
3.92-3.96
3.88-3.91
3.84-3.87
3.80-3.83
3.76-3.79
3.72-3.75
3.67-3.71
3.63-3.66
3.59-3.62
4.58
4.51-4.58
4.46-4.50
4.42-4.45
4.38-4.41
4.34-4.37
4.30-4.33
4.26-4.29
4.21-4.25
4.17-4.20
4.13-4.16
4.09-4.12
4.05-4.08
4.01-4.04
3.97-4.00
3.92-3.96
3.88-3.91
3.84-3.87
3.80-3.83
3.76-3.79
3.72-3.75
3.67-3.71
3.63-3.66
3.59-3.62
0 3.24
3.16-3.24
3.12-3.15
3.07-3.11
3.03-3.06
2.98-3.02
2.94-2.97
2.90-2.93
2.85-2.89
2.81-2.84
2.77-2.80
2.72-2.76
2.68-2.71
2.64-2.67
2.59-2.63
2.55-2.58
2.50-2.54
2.46-2.49
2.42-2.45
2.37-2.41
2.33-2.36
2.29-2.32
0 4.20
4.12-4.20
4.08-4.11
4.04-4.07
3.99-4.03
3.95-3.98
3.91-3.94
3.86-3.90
3.82-3.85
3.78-3.81
3.73-3.77
3.69-3.72
3.64-3.68
3.60-3.63
3.56-3.59
3.51-3.55
3.47-3.50
3.43-3.46
3.38-3.42
3.34-3.37
3.30-3.33
3.25-3.29
0 5.30
5.22-5.30
5.18-5.21
5.14-5.17
5.09-5.13
5.05-5.08
5.01-5.04
4.96-5.00
4.92-4.95
4.88-4.91
4.83-4.87
4.79-4.82
4.75-4.78
4.70-4.74
4.66-4.69
4.62-4.65
4.57-4.61
4.53-4.56
4.48-4.52
4.44-4.47
4.40-4.43
4.35-4.39
0 4.33
4.25-4.33
4.21-4.24
4.16-4.20
4.12-4.15
4.08-4.11
4.03-4.07
3.99-4.02
3.95-3.98
3.90-3.94
3.86-3.89
3.82-3.85
3.77-3.81
3.73-3.76
3.69-3.72
3.64-3.68
3.60-3.63
3.56-3.59
3.51-3.55
3.47-3.50
3.43-3.46
3.38-3.42
0 4.23
4.16-4.23
4.11-4.15
4.07-4.10
4.03-4.06
3.98-4.02
3.94-3.97
3.90-3.93
3.85-3.89
3.81-3.84
3.77-3.80
3.72-3.76
3.68-3.71
3.63-3.67
3.59-3.62
3.55-3.58
3.50-3.54
3.46-3.49
3.42-3.45
3.37-3.41
3.33-3.36
3.29-3.32
0 5.42
5.35-5.42
5.31-5.34
5.27-5.30
5.23-5.26
5.18-5.22
5.14-5.17
5.10-5.13
5.06-5.09
5.02-5.05
4.98-5.01
4.94-4.97
4.89-4.93
4.85-4.88
4.81-4.84
4.77-4.80
4.73-4.76
4.69-4.72
4.64-4.68
4.60-4.63
4.56-4.59
4.52-4.55
4.48-4.51
4.43-4.47
5.42
5.35-5.42
5.31-5.34
5.27-5.30
5.23-5.26
5.18-5.22
5.14-5.17
5.10-5.13
5.06-5.09
5.02-5.05
4.98-5.01
4.94-4.97
4.89-4.93
4.85-4.88
4.81-4.84
4.77-4.80
4.73-4.76
4.69-4.72
4.64-4.68
4.60-4.63
4.56-4.59
4.52-4.55
4.48-4.51
4.43-4.47
0 4.33
4.25-4.33
4.20-4.24
4.16-4.19
4.12-4.15
4.07-4.11
4.03-4.06
3.99-4.02
3.94-3.98
3.90-3.93
3.85-3.89
3.81-3.84
3.77-3.80
3.72-3.76
3.68-3.71
3.64-3.67
3.59-3.63
3.55-3.58
3.51-3.54
3.46-3.50
3.42-3.45
3.37-3.41
0
