The chain of custody establishes a documented record of how a specimen is collected, identified, handled and transferred for testing. It helps demonstrate that the specimen tested belongs to the correct individual and has been properly accounted for throughout the process.

If the chain of custody is incomplete or a discrepancy arises, the integrity of the specimen and reliability of the result may be questioned. Depending on the circumstances and the applicable testing protocol, the result may require further investigation, may not be accepted, or may need to be cancelled and the test repeated.

For HR, this can have significant consequences. A result that cannot be adequately supported may be difficult to rely on when making employment decisions, particularly following a workplace incident or where disciplinary action is being considered.

The key point: Chain of custody is not simply paperwork. It is an essential part of establishing the credibility of the test result.

An initial drug screen is designed to identify specimens that may contain a target drug or its metabolites. A non-negative result indicates that further assessment may be required; it does not, by itself, establish confirmed drug use.

Certain screening methods can react to other substances, including some medications. A confirmation test uses a more specific analytical method to determine whether the target substance is present.

Where required by the testing protocol, the specimen should undergo confirmatory analysis before the result is treated as confirmed positive. The findings should then be reviewed through the applicable MRO process.

HR should establish the status of the result before taking action. Treating a preliminary screening result as conclusive evidence of misconduct can lead to unfair decisions and avoidable disputes.

A confirmation test provides more specific analytical evidence than an initial screening test. It helps distinguish a preliminary non-negative finding from a result supported by a more specific testing method.

This distinction is particularly important when the outcome could affect an employee’s job, professional standing or continued deployment in a safety-sensitive role.

The appropriate process is to follow the relevant testing protocol, obtain confirmatory analysis where indicated, and complete the required MRO review before drawing conclusions about the result.

A confirmed laboratory finding should still be interpreted in context. The MRO review helps determine whether a legitimate medical explanation or a procedural issue affects the final outcome.

Yes. Certain prescription or other medications may cause a non-negative initial screening result, depending on the substance and the testing method used.

This is one reason an initial screening result should not automatically be interpreted as evidence of illicit drug use or misconduct.

Where appropriate, the MRO can contact the employee to establish whether a legitimate medical explanation accounts for the finding. Relevant information can then be assessed as part of the result-verification process.

HR generally does not need to independently interpret an employee’s medication history or make a medical judgement about the test. The MRO’s role is to assess the medical explanation and communicate the appropriate verified outcome, while protecting confidential medical information.

An employee’s dispute should be handled through a documented and impartial review process rather than resolved solely through an internal HR assessment.

HR should establish:

• Whether the initial result was confirmed according to the applicable protocol.
• Whether specimen identification and chain-of-custody records are complete.
• Whether the employee has raised a possible medical explanation.
• Whether the testing programme provides for further analysis, such as testing a retained specimen, and whether the relevant conditions and time limits can be met.
• Whether the MRO has completed the required review and whether any procedural discrepancy remains unresolved.

The appropriate follow-up will depend on the testing method, the specimen arrangements and the applicable programme requirements.

Maintaining clear records and allowing the established review process to run its course helps the employer handle disputes fairly and consistently.

Where drug or alcohol impairment is suspected following a workplace incident, the immediate priority is to protect employees and others from further harm.

The employer should follow its incident-management and drug and alcohol policies, assess any immediate safety risk, and consider appropriate interim measures for safety-sensitive duties.

If testing is indicated, it should be arranged promptly in accordance with the applicable protocol. HR should ensure that the collection, documentation and chain-of-custody requirements are followed, and that the result is reviewed appropriately before drawing conclusions.

A suspected incident, observed behaviour or preliminary screening result should not automatically be treated as proof of drug use. The findings must be assessed through the relevant testing and review process.

HR needs sufficient information to make appropriate workplace decisions, but does not necessarily need access to an employee’s full medical history.

The MRO’s report should communicate the verified outcome in accordance with the applicable testing programme. Where relevant, the MRO may also identify a result that cannot be verified or a procedural issue that requires further attention.

The employer can then determine the appropriate employment or operational response under its company policy and applicable requirements.

Access to test results and related records should be limited to authorised personnel. Medical details should be handled confidentially and disclosed only where appropriate.

This separation of medical review from employment decision-making helps protect employee privacy while giving HR a more reliable basis for action.

Not automatically. The appropriate response depends on the role, the circumstances, the applicable company policy and the nature of the result.

Where there is a credible immediate safety concern, an employer may need to remove the employee temporarily from safety-sensitive duties while the matter is assessed. Any interim action should be proportionate, consistent with company policy and applicable requirements, and should not be presented as a final finding of misconduct.

HR should distinguish between immediate risk management and the final interpretation of the test result. The MRO review and any required confirmation testing should proceed through the appropriate process before the employer makes a final decision.

A screening programme should be designed around clear procedures, trained personnel and consistent documentation—not simply the choice of drug panel.

Before implementation, HR should ensure that the company has a written policy explaining when testing may be conducted, how results will be handled, what happens after a non-negative result, and how confidentiality will be maintained.

The employer should also establish who is responsible for specimen collection, chain-of-custody documentation, confirmatory testing, MRO review and communication of results.

Using a consistent process across departments, sites and contractors helps reduce procedural inconsistencies and makes it easier to identify and address problems before they undermine a result.

The aim is to ensure that employees are treated consistently and that decisions are based on properly obtained, reviewed and documented findings.