> For the complete documentation index, see [llms.txt](https://railnology.gitbook.io/railnology-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://railnology.gitbook.io/railnology-docs/drug-and-alcohol-testing/understanding-results.md).

# Understanding Test Result Types

Railnology supports all DOT-defined drug and alcohol test result classifications under 49 CFR Part 40.

## Result Types

| Result          | Definition                                                              |
| --------------- | ----------------------------------------------------------------------- |
| Negative        | No prohibited substance detected above threshold                        |
| Dilute Negative | Negative result but specimen was dilute — may require retest per policy |
| Non-Negative    | Presumptive positive — requires MRO confirmation                        |
| Positive        | MRO-confirmed positive result                                           |
| Refusal         | Employee refused to submit to testing                                   |
| Adulterated     | Specimen contained a substance not expected in human urine              |
| Substituted     | Specimen not consistent with normal human urine                         |
| Cancelled       | Test cancelled — result cannot be used (administrative or lab error)    |

## Removal Trigger

Railnology automatically flags **Removal Required** for the following result types: Positive, Refusal, Adulterated, Substituted.

Dilute Negative and Cancelled results do not trigger automatic removal but should be reviewed by the administrator per your railroad's policy.

## Regulatory Reference

* 49 CFR Part 40 — DOT Procedures for Transportation Workplace Drug and Alcohol Testing Programs
* 49 CFR Part 219 — Control of Alcohol and Drug Use in Railroad Operations