When SPF Results Disagree: A Disciplined Path From Doubt to Decision

Two laboratories, two very different SPF results. Dr Leslie Laquieze sets out a seven-step escalation pathway that helps sponsors find the cause and make a defensible claim decision, without falling into the trap of testing until they get the answer they want.

By Dr Leslie Laquieze, PharmD, MSc, PhD, MBA, Expert Member, Australian Sunscreen Council

Discordant SPF results are not rare. The Therapeutic Goods Administration’s March 2026 consultation paper on improving sunscreen regulation describes “significant variability” in results from the current in-vivo method, increasing as SPF values increase. The TGA’s consumer information page records that its investigation of the 2025 CHOICE results “involves investigating the reasons for inconsistent SPF test results across the CHOICE testing and testing evidence held by sponsors.”

The TGA acknowledges this. In its statement on the CHOICE SPF sunscreen findings, it said: “It is a known issue that there is variability in SPF testing results across laboratories because testing on humans can be highly subjective and the response to a test can differ dramatically from one individual to another.” Its Advice for sunscreen sponsors and manufacturers states that “where multiple tests have produced different SPF results, these factors may be considered by the TGA when weighing the totality of evidence submitted for SPF indications.” A TGA presentation on improving sunscreen regulation adds that “it is impractical and unrealistic to expect each and every batch of a sunscreen to hit the target SPF exactly every time.”

In the author’s opinion, a single low result should be investigated, not treated as conclusive. Because of the variability of the in-vivo method, a consistent pattern of low results across several reliable tests is needed before an SPF claim can properly be called into question. The question is not whether discordant results will occur, but whether a company has a procedure ready before they do.

The seven-step escalation pathway

1. Confirm sample identity and handling. Check the product, batch, formula version, manufacturing process and packaging of every sample tested. SPF results also depend on how the tested sample was treated: whether it was stored at the correct temperature, protected from heat and light, kept within its shelf life, mixed as directed and transported under controlled conditions. The TGA’s advice lists “records ensuring traceability of sample handling during testing” among the documents that support reliability. Many apparent discrepancies turn out to involve different batches, a superseded formula or a sample that was stored badly.

2. Check the laboratory and the execution. Check the credentials of each laboratory that did the testing. Ask for its testing procedure, the qualifications and training of the technicians who applied the product, and evidence that a uniform layer was applied. The TGA’s advice lists “evidence of staff training and competency for SPF testing methods” among the supporting documents. Do this for your original test data as well as the new data. Review validity criteria, exclusions and individual subject data, not only the final mean, together with drying time, reference sunscreen results and irradiator calibration.

3. Check the supply chain. Has the supplier, grade or specification of any active ingredient changed since the original test? A change in a UV filter’s source, particle size, coating, purity or impurity profile can change performance even when the formula on paper is unchanged. Sunscreen active ingredients manufactured in Australia are generally made under a TGA manufacturing licence; the TGA’s user guide on Australian manufacturing licences and overseas GMP certification covers “Australian manufacturers of therapeutic goods (medicines, active pharmaceutical ingredients (APIs)…)”. Requirements for overseas sites depend on the manufacturing step and whether that step must be recorded in the ARTG entry. The TGA’s GMP clearance guidance should therefore be applied to the specific supply chain rather than summarised as a general exemption or approval. In all cases, the sponsor and manufacturer remain responsible for supplier qualification, specifications, certificates of analysis, change notification and risk-based incoming testing.

4. Review the formulation science. Examine filter dispersion, emulsion stability, rheology, volatility, density, film formation and any interaction with packaging. A product that separates, a filter that crystallises or a film that forms unevenly will test differently between laboratories and over time.

5. Use an orthogonal method to locate the cause. In-vitro methods such as ISO 23675:2024 and ISO 23698:2024 can help determine whether the problem lies in the product or in the test. The TGA’s Advice for sunscreen sponsors and manufacturers confirms that sponsors may hold such additional evidence. Do not, however, assign an investigational method a regulatory status it does not have.

6. Apply a predefined retest plan. If material uncertainty remains, retest according to a plan written before the discrepancy occurred, and consider a second qualified laboratory. The plan should define how many tests, at which laboratories and how all results will be weighed, including unfavourable ones.

7. Decide and document. Record the claim decision, the rationale, CAPA and any required label, ARTG or market action. If the evidence no longer supports the claim, the claim must change.

Weighing results honestly

All valid results belong in the evidence file. A credible weighting considers laboratory competence and accreditation, method version, traceability of the sample, completeness of the data and the plausibility of individual values. The TGA’s tiered laboratory ranking, set out in its September 2025 advice, provides a useful framework. Results from laboratories at the top of the ranking should generally carry more weight than those from laboratories at the bottom.

Real consequences

Australian experience shows where unresolved discrepancies can lead. The TGA’s page on sunscreens using the same base formulation as Ultra Violette Lean Screen records voluntary cancellations, TGA-initiated cancellations and recalls required under section 30EA of the Therapeutic Goods Act 1989. A documented investigation pathway, applied early, gives a sponsor the best chance of resolving a problem on its own terms.

Write the procedure now

A discordant-result procedure should be approved before a product is launched. It should name who is responsible, set timeframes, define when a product must be quarantined or a claim suspended, and specify when the TGA must be informed. Combined with retained samples and complete laboratory data, it turns a crisis into a manageable quality event.

Sources

·         Therapeutic Goods Administration, consultation paper, March 2026: https://consultations.tga.gov.au/tga/improvements-to-regulation-of-sunscreens-in-aus/user_uploads/final---consultation---seeking-feedback-on-improvements-to-the-regulation-of-sunscreens-in-australia---v1-march-2026-2.pdf

·         Therapeutic Goods Administration, “Sunscreen SPF testing – information for consumers”: https://www.tga.gov.au/resources/explore-topic/sunscreens/sunscreen-spf-testing-information-consumers

·         Therapeutic Goods Administration, “TGA statement on CHOICE SPF sunscreen findings”, 12 June 2025: https://www.tga.gov.au/news/news-articles/tga-statement-choice-spf-sunscreen-findings

·         Therapeutic Goods Administration, “Improving the regulation of sunscreens in Australia”, presentation, April 2026: https://www.tga.gov.au/sites/default/files/2026-04/presentation-improving-the-regulation-of-sunscreens-in-australia.pdf

·         Therapeutic Goods Administration, “Australian manufacturing licences and overseas GMP certification”: https://www.tga.gov.au/resources/resources/user-guide/australian-manufacturing-licences-and-overseas-gmp-certification

·         Therapeutic Goods Administration, “GMP Clearance Guidance”, V18.4, November 2023: https://www.tga.gov.au/sites/default/files/2023-12/gmp-clearance-guidance.pdf

·         Therapeutic Goods Administration, “Advice for sunscreen sponsors and manufacturers”, 23 September 2025: https://www.tga.gov.au/products/medicines/therapeutic-sunscreens/manufacturing/advice-sunscreen-sponsors-and-manufacturers-acceptance-additional-spf-testing-information

·         Therapeutic Goods Administration, “Sunscreens using the same base formulation as Ultra Violette Lean Screen SPF 50+ sunscreen”: https://www.tga.gov.au/resources/explore-topic/sunscreens/sunscreens-using-same-base-formulation-ultra-violette-lean-screen-spf-50-sunscreen

About the Author

Dr Leslie Laquieze (PharmD, MSc, PhD, MBA) is a pharmacist-scientist and international expert in sunscreen testing, photoprotection, skin pharmacology and dermocosmetic claim substantiation. An expert member of the Australian Sunscreen Council, she has led Kosmoscience Europe since 2018, supporting the evaluation, substantiation and regulatory positioning of cosmetic and dermatological products across international markets.

This article reflects the opinion of Dr Leslie Laquieze. Readers are recommended to seek expert legal advice on all issues discussed.