Understanding “Presumptive Positive” Results
At EMSL Analytical, Inc., we are committed to providing you with accurate and timely analytical results. As part of our testing process, you may encounter the term “Presumptive Positive” in your laboratory report. Below, we’ve outlined what this term means and how you can interpret it.
What is a Presumptive Positive?
A Presumptive Positive result indicates that the initial screening or test has detected the potential presence of a target organism, substance, or contaminant. This result suggests that the sample may contain the analyte of interest but requires additional confirmation or analysis for definitive identification.
Why is it Called “Presumptive”?
- The initial test or screening is designed to be highly sensitive to detect even small amounts of the target.
- While sensitive, the screening may occasionally detect substances that mimic the target, leading to a presumptive positive.
- To confirm the result, further analysis or more specific testing may be necessary.
What Happens Next?
If a presumptive positive is reported, EMSL Analytical will typically recommend or automatically proceed with confirmatory testing (depending on your testing agreement). This secondary testing will:
- Validate the initial findings.
- Provide conclusive identification and/or quantification of the target.
Common Applications for Presumptive Positive Results
Presumptive positives are often encountered in the following testing scenarios:
- Microbiological Testing: Detection of bacteria, mold, or pathogens.
- Example: A presumptive positive for Legionella suggests that initial testing detected the potential presence of Legionella species.
- Environmental Testing: Screening for contaminants in air, water, or soil.
- Example: A presumptive positive for asbestos fibers means initial analysis suggests the presence of asbestos.
- Food Safety Testing: Detection of pathogens like Salmonella or Listeria.
- Example: A presumptive positive for Salmonella indicates the need for confirmatory culture testing.
Key Points to Remember
- A presumptive positive does not guarantee the presence of the target but serves as an initial indication.
- Confirmatory testing is required to definitively identify the target substance or organism in the sample.
- EMSL Analytical is here to provide guidance and ensure that your results are accurate and actionable.
Contact Us for Support
If you have any questions about your results or need assistance understanding a presumptive positive report, please don’t hesitate to reach out:
Phone: (800) 220-3675
Website: www.emsl.com
English 
French 
Spanish 
Portuguese