Debrief: what this pattern supports, and what stays open

What is supported: TSH and free T4 direction, read together, classify a result into primary hypothyroid, primary hyperthyroid, or central hypothyroid patterns, and a discordant pair is a real, actionable signal to investigate rather than a value to explain away. A concordant alternate-platform result after an appropriate washout supports interference as the working explanation for a discordant pattern.

What is not supported: the paired results do not establish a specific diagnosis such as Graves disease or a toxic nodule, do not authorize a medication dose change from one unconfirmed result, and do not imply that biotin interference always moves TSH low and T4 high, because the direction depends on assay format and must be confirmed against the specific platform's package insert.

What depends on method or local policy: the exact biotin washout duration and dose threshold, the pregnancy trimester TSH reference interval when a validated local range is unavailable, the PEG-precipitation recovery cutoff, and the reflex algorithm for adding FT4, T3, or antibodies after an abnormal TSH are all declared, laboratory-specific values rather than universal constants, and a real deployment must substitute its own validated numbers before this content trains staff on an actual bench.

Federal and consensus framing: under 42 CFR 493.1291, a CLIA-certified laboratory must make interference information available to clients on request and must provide interpretive information affecting test results, including pertinent updates when they change; CLSI EP07 is the consensus framework for designing, screening, and confirming analytical interference, and it explicitly excludes physiological states such as pregnancy from its definition of interference, which is why pregnancy is handled as a reference-interval question rather than an interference question.

When a thyroid result does not fit the pattern the clinical picture predicts, the laboratory's job is to say so precisely, and to investigate before the number is used to change a patient's treatment.