What to do when laboratory test results conflict
Pause the affected stock decision and compare the complete reports before ordering more tests. Establish whether the samples, methods, conditioning, units and acceptance rules match, then agree a controlled investigation of the remaining difference. Factory records and sample collection can be coordinated by Cambridge China Bridge.
Establish what each laboratory actually tested
Request complete reports, sample receipt records, photographs and the submitted testing briefs. Match the factory, batch, product revision, material, colour and component tested. Identical catalogue descriptions do not establish identical samples. Check whether each laboratory received finished goods, loose components or material specially prepared by the factory.
Trace who selected each sample, where it came from and whether it was altered before testing. Separate missing identity evidence from a genuine difference in results. Use sample chain of custody for the handling record and checking report coverage for the connection to your order.
Compare methods and conditioning
Ask each laboratory to identify the exact method, edition, test clause and any deviation. Compare specimen preparation, equipment settings, extraction procedures and the property being measured. Testing a surface coating and testing the whole component can answer different questions even when the report headings look similar.
Compare conditioning temperature, humidity and duration, together with storage, transport, washing, curing and ageing history. For functional tests, also check loading, mounting, power supply and operating settings. Ask the laboratories to explain which differences could affect the result before agreeing a repeat test.
Separate the measurement from the pass decision
Put the reported values beside their units, calculation basis and acceptance limits. Check whether results refer to dry material, material as received, a surface area or the complete item. Ask a laboratory to verify any conversion. A result below a reporting limit is not automatically zero; request the detection and quantification limits where relevant.
Compare the specified acceptance criterion, rounding and the rule used to account for measurement uncertainty. Ask whether the disagreement is in the measured values or only in the pass decision. Environment Agency water-monitoring guidance recognises that sampling can materially affect measurement uncertainty. For goods, ask the laboratories to assess the relevant contribution rather than assuming that a small difference proves an error.
Commission an investigation that can explain the difference
Send both laboratories the comparison record and ask for written explanations of unresolved differences. Agree the investigation question, method, conditioning, reporting units, acceptance criterion and interpretation of uncertainty before samples are tested. Check the proposed provider against laboratory accreditation for your tests. A fresh pass report alone does not explain the earlier failure.
Have a competent specialist design representative sample selection and coded distribution. Agree whether material can be homogenised and split without changing the property, or whether matched finished items are needed. Retain sealed reserve samples and record every transfer. Consider repeat measurements and suitable control material; require raw results, deviations and a comparison with the original reports.
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Keep stock decisions separate from investigation findings
As a precaution, segregate affected stock and pause its release while an unresolved safety concern is assessed. Preserve the original reports and correspondence. Do not average incompatible results, discard the unfavourable report or keep commissioning tests until a pass appears. Escalate a safety concern to a product specialist without waiting for the comparison exercise to finish.
Record the explanation, the affected batches and the evidence supporting the eventual stock decision. An investigation may identify sample variation, method differences or a reporting error, or remain inconclusive. Cambridge China Bridge can coordinate factory records and sample collection through its own staff in China, using the agreed laboratory brief.
Frequently asked questions
Should I order another laboratory test straight away?
First compare sample identity, methods, conditioning, units and acceptance rules. Commission more testing when you can state what unresolved difference it should investigate.
Does a passing report cancel a failing report?
Keep both reports. Establish why they differ and whether each applies to the affected goods before using either to support a stock decision.
Can laboratories test the same physical sample?
Sometimes, but destructive testing or changed conditioning may prevent a fair comparison. Ask a specialist whether split material or matched finished items would be suitable.
Who should pay for the investigation?
Agree payment with the seller and laboratory before commissioning work. Record the scope, reporting access and how costs will be addressed once the cause is established.