United States Department of Agriculture

Agricultural Marketing Service, Science & Technology

Microbiological Data Program

SOP No.: MDP-QA-02 Page 1 of 4

Title: Proficiency Test Samples

Revision: 04 Replaces: 09/25/09 Effective: 10/01/10

1. Purpose

To provide guidance for the analysis of Proficiency Test (PT) samples by laboratories 

participating in the Microbiological Data Program (MDP).

2. Scope

This Standard Operating Procedure (SOP) shall be followed by all laboratories conducting 

microbiological studies for MDP, including support laboratories conducting non-routine 

activities that may impact the program.

3. References

3.1. Current MDP Semi-Annual Program Plan

3.2. Current MDP SOPs

4. Procedures

4.1. Proficiency Testing Round

4.1.1. MPO reserves the right to accept or reject results of MDP laboratories participating 

in PTs administered by outside Federal agencies such as FERN or the FDA. Once 

MPO agrees to accept a round of outside PT results, MDP laboratories will adhere 

to procedures set forth by the administering federal agency for that PT round. If 

MPO does not agree to accept outside PT results, the MDP laboratories will 

proceed with the following steps of this SOP.

4.1.2. If required, PT samples shall be inoculated by the laboratory Quality Assurance 

Officer (QAO) or designee and transferred to the Technical Program Manager 

(TPM) or designee for analysis.

4.1.3. PT samples shall be analyzed by the technical group according to the latest MDP 

Semi-annual Program Plan and the MDP SOPs currently in use in the same manner 

as regular MDP samples.

4.2. Test Sample Analysis

4.2.1. Sample analysis shall begin as stated per provided PT protocol(s).
United States Department of Agriculture

Agricultural Marketing Service, Science & Technology

Microbiological Data Program

SOP No.: MDP-QA-02 Page 2 of 4

Title: Proficiency Test Samples

Revision: 04 Replaces: 09/25/09 Effective: 10/01/10

4.2.2. Samples shall be analyzed according to MDP SOP(s) currently in use. 

4.2.3. Routine media and cultural controls shall accompany the analysis and be processed 

per applicable MDP SOPs.

4.2.4. Laboratories shall attempt confirmation of any presumptive positive samples 

according to the appropriate cultural procedures for that test organism. Cultural 

confirmation will not be required for any MPO supplied competing background 

organism(s).

4.3. Reporting PT Results

4.3.1. Analysts are responsible for recording test results on the reporting form(s)supplied 

with each PT round. These results shall be reported to the QAO or designee in 

sufficient time for the QAO/designee to add inoculation concentrations, 

review/verify results, and meet MPO’s reporting deadline.

4.3.2. QAO or designee shall report PT results to MPO by the specified reporting date.
United States Department of Agriculture

Agricultural Marketing Service, Science & Technology

Microbiological Data Program

SOP No.: MDP-QA-02 Page 3 of 4

Title: Proficiency Test Samples

Revision: 04 Replaces: 09/25/09 Effective: 10/01/10

Mary Tijerina 1 September 2010

___________________________________________________________

Revised by: Mary Tijerina Date

Microbiologist, Monitoring Programs Office

8609 Sudley Road, Suite 206

Manassas, VA 20110

(703) 330-2300x111

Shanker Reddy 2 September 2010

___________________________________________________________

Reviewed by: Shanker Reddy Date

Molecular Biologist, Monitoring Programs Office

8609 Sudley Road, Suite 206

Manassas, VA 20110

(703) 330-2300x135

Diana Haynes 2 September 2010

Approved By: Diana Haynes Date

Deputy Director, Monitoring Programs Office

8609 Sudley Road, Suite 206

Manassas, VA 20110

(703) 330-2300x134

ORIGINAL SIGNATURE PAGE MAINTAINED BY USDA, AMS, SCIENCE & TECHNOLOGY, MONITORING PROGRAMS OFFICE

ELECTRONICALLY REPRODUCED SIGNATURES
United States Department of Agriculture

Agricultural Marketing Service, Science & Technology

Microbiological Data Program

SOP No.: MDP-QA-02 Page 4 of 4

Title: Proficiency Test Samples

Revision: 04 Replaces: 09/25/09 Effective: 10/01/10

Revision 04 August 2010 Monitoring Programs Office

 Deleted Old Section 4.1.1., “PT samples shall be analyzed according to the latest MDP 

Semi-Annual Program Plan and the MDP SOPs currently in use” and replaced with

“MPO reserves the right to accept or reject results of MDP laboratories participating in 

PTs administered by outside Federal agencies such as FERN or the FDA. Once MPO 

agrees to accept a round of outside PT results, MDP laboratories will adhere to 

procedures set forth by the administering federal agency for that PT round. If MPO does 

not agree to accept outside PT results, the MDP laboratories will proceed with the 

following steps of this SOP.”

 Added the words “If required...”, Section 4.1.2.

 Revised Section 4.1.3. to read as “PT samples shall be analyzed by the technical group 

according to the latest MDP Semi-annual Program Plan and the MDP SOPs currently in 

use in the same manner as regular MDP samples.”

Revision 03 September 2009 Monitoring Programs Office

 Revised Section 1, Purpose

 Revised Section 4, Procedures

Revision 02 February 20008 Monitoring Programs Office

 Revised to allow technical group or QAU to purchase produce for PT rounds

Revision 01 December 2005 Monitoring Programs Office

 Updated to reflect current PT practices and requirements.