What to Do When You Receive an Out of Specification (OOS) Result

Unexpected test results can raise important questions for any Quality Assurance team.

Perhaps the reported THC potency is lower than expected. Maybe the terpene profile doesn’t align with previous harvests or the cultivar’s expected characteristics. Whatever the case, an unexpected result doesn’t necessarily mean something has gone wrong.

Before making production decisions or assuming laboratory error, it’s important to take a structured approach to understanding the result.

Use the Opportunity to Look at the Bigger Picture

An unexpected result is often more valuable than it first appears.

Routine testing creates a historical record that allows QA teams to identify trends over time. Comparing data across multiple batches can reveal gradual changes in potency, terpene profiles, moisture, or other quality attributes that may not be obvious from a single Certificate of Analysis.

Historical data can help answer important questions, including:

· Is this an isolated result?

· Is potency gradually shifting over multiple batches?

· Are terpene profiles changing over time?

· Has a recent process change affected product consistency?

· Are there early indicators that warrant further investigation?

Trend analysis transforms routine analytical testing into a proactive quality management tool, helping producers identify changes early and make informed decisions before minor variations become larger challenges.

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Step 1: Determine Whether the Result Makes Sense

A Certificate of Analysis reflects the specific sample submitted for testing. Before requesting additional testing, consider whether there may be a reasonable explanation for the result.

Ask yourself:

· Was the submitted sample representative of the entire batch?

· Have there been any changes to cultivation, harvest timing, drying, curing, or storage?

· Have similar trends appeared in recent batches?

· Does the result align with other quality indicators?

Unexpected results are often linked to natural biological variation or sampling rather than analytical error. Taking a systematic approach to reviewing the result can help determine the most appropriate next step.

Step 2: Confirmation using Retained Material

If your potency result is only slightly outside your expected specification, an internal confirmation may be the most appropriate first step.

PPB Analytical can reanalyze the retained portion of the original sample using the same validated analytical methodology. The reported result is based on the average of both analyses in accordance with our internal quality procedures.

Because the same retained sample is being analyzed, only minor differences in potency would typically be expected. Internal confirmation is designed to verify the reproducibility of the original analysis rather than produce a substantially different result.

Internal confirmation is best suited for situations where the result is only slightly outside expectations and you would like additional confidence before making a production decision.

Step 3: Full Retest with Additional Material

Sometimes, a fresh sample provides the most meaningful answer.

If the potency result is significantly outside your expected specification, submitting a new sample for a complete retest is generally the better option. A fresh sample repeats the entire analytical process from the beginning, including sample preparation, and provides a new assessment of the batch.

A new sample is also recommended when:

· The original sample may not have been representative of the lot.

· Sampling variability is suspected.

· Confirmation of a terpene profile is required.

Terpenes are naturally volatile compounds, and a portion is consumed during the original analytical process. Because of this, reanalyzing the retained sample may not accurately reflect the original terpene profile. Testing a fresh sample provides the most reliable assessment.

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Choosing the Right Next Step

Scenario	Recommended Action
Potency is slightly outside your expected specification	Confirmation using Retained Material
Potency is significantly outside your expected specification	Submit a new sample for a complete retest
Confirmation of terpene results is required	Submit a new sample for a complete retest
Sampling concerns or batch variability are suspected	Submit a new sample for a complete retest

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PPB’s Recommendation

When an unexpected result is received, avoid rushing to conclusions.

Review the result in the context of your production process, consider whether the submitted sample was representative of the batch, and choose the follow-up that will provide the most meaningful information. An internal confirmation can provide additional confidence when a potency result is only slightly outside expectations, while a complete retest using a fresh sample is generally the better option for more significant differences or when evaluating terpene profiles.

At PPB Analytical, we believe analytical testing is about more than delivering a Certificate of Analysis. It’s about providing reliable data, practical guidance, and the confidence to make informed quality decisions.