(Originally presented August 25, 2011)

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# DISCLAIMER This information is distributed solely for the purpose of pre- dissemination peer review under applicable information quality guidelines. It has not been formally disseminated by EPA. It does not represent and should not be construed to represent any Agency Determination or Policy . The information provided should not be cited or referenced. For Official Use Only/Do not Cite or Distribute

# Presentation Overview

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###  

## Overall goal  

## Available data  

## Method performance and product performance  

## 2009 collaborative study design  

## The data and use of the MPN formula  

## Identifying sources of variability

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# Overall Goals of the Reassessment  

### Short - term/mid - term solution while we implement OECD method  

### Use the best data available and apply the best available statistics  

### Include input from stakeholders, i.e., the EWG  

### Seek independent technical assessment, e.g., AOAC  

### Incorporate critical UDM revisions  

### If approved, provide detailed communication and instructions to end - users  

### Ensure long term monitoring process 4 For Official Use Only/Do not Cite or Distribute

# Available Data  

# Data available for analysis from recent 5 - lab collaborative study with industry  

## Originally designed with industry to assess method modifications, proposed to resolve the pellicle issue.  

## MLB was the lead lab; 1 contract lab and three industry labs  

## The modifications were shown not to improve the UDM; however, the current UDM exhibited acceptable performance overall. 5 For Official Use Only/Do not Cite or Distribute

# Contrasting Method Performance and Product Performance

 

### Method Performance  Method’s ability to generate consistent and reproducible data under typical lab situations  Enhanced by following standard methods and SOPs  Variability between UDM tests within a lab and between labs, of the same product  Control counts  Responsiveness to changes in product effectiveness 

###  

### Product Performance  Efficacy – using qualitative and quantitative tests  Per formulation type  Per label claims and test conditions  Neutralization critical to measuring efficacy

6 For Official Use Only/Do not Cite or Distribute**Microbe Day**  **1 (Rep #1)**  **Day 2 (**  **Rep #2) Day**  **3 ( Rep #3)**  S. aureus Test 1: Current UDM Test 1: Current UDM Test 1: Current UDM Test 2: Modified UDM Test 2: Modified UDM Test 2: Modified UDM P. aeruginosa **Day 4 (**  **Rep #1) Day**  **5 ( Rep #2)**  **Day 6 (**  **Rep #3)** Test 1: Current UDM Test 1: Current UDM Test 1: Current UDM Test 2: Modified UDM Test 2: Modified UDM Test 2: Modified UDM
• Use of MLB’s SOP •One QAC product with the label claim • Five highly representative labs •60 - carrier tests •6 log minimum carrier count •A total of 30 tests utilized in the reassessment •Order of microbe randomized 

# Basic Study Design for the 2009 Use - dilution method Collaborative

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# Data from the 2009 collaborative A. Numbers of positive carriers out of 60

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# Data from the 2009 Collaborative B. Control carrier log densities ( mean +/- 1 SEM)

For Pa, SEM = 0.14; for Sa, SEM = 0.12. For Official Use Only/Do not Cite or DistributeCarrier counts in combination with the number of

positives
log reduction (LR) 

## For statistical analysis, conversion of number of positives to log reduction values – use of the MPN formula

Use of the MPN formula

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# Use of the MPN formula  

## Widely used by FDA – see Blodgett, R.J., (2006) Most Probable Number Determination from Serial Dilutions. FDA’s Bacteriological Analytical Manual  

## Used by EPA in the past – see Tomasino and Hamilton (2006). Modification to the AOAC Sporicidal Activity of Disinfectants Test: Collaborative Study. JAOAC Int. 89:1373 - 1397  

## See MSU’s “Knowledge Sharing Article” KSA- SM - 08 for complete details on the P/N formula at http://www.biofilm.montana.edu/content/ksa - sm - 08
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### within - lab variability 

# Identifying sources of variability

For Official Use Only/Do not Cite or Distributemean LR is 8.26

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### Among - lab variability 

# Identifying sources of variability

For Official Use Only/Do not Cite or DistributeWithin - lab variability Among- lab variability **Reproducibility SD = 0.5348** 

# Identifying sources of variability

Using an assessment variability, we can develop

the probability of events through modeling For Official Use Only/Do not Cite or Distribute

### For 60 carrier UDM tests, P/N LR values are displayed for each combination of the observed number of positive carriers

16 60 50 40 30 20 10 0 8.5 8.0 7.5 7.0 6.5 6.0 No. PositiveP/NLR P/N LR for 60 carrier UDM when the mean control LD = 6.5

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# Important Questions to Ask  

## Type 1 Error  

### How often does a marginally ineffective product pass?  

### Example: using the current performance standard of allowing 0 - 1 positive  

### Example: using a new performance standard 

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## Type 2 Error  

## How often does a highly effective product fail?

 

### Example: using the current performance standard  

### Example: using a new performance standard

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# Overall Recommendations

Increased confidence in the outcome Revise performance standards for each microbe Require multiple testing of the same product Use other enhancements to the UDM such as max. carrier counts

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# Additional technical review  

## Manuscript for JAOAC describing procedural revisions and the proposed performance standards under preparation  

### Submit to JAOAC  

### Independent panel of experts is assigned for review

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