dromlakhani Maintain consistent GH and IGF-1 assay throughout management
STEP 1 — Gather Information
Retrieve any previous GH and IGF-1 results and record the assay method and laboratory used.
STEP 2 — Rule In / Rule Out
Is there a documented prior assay for this patient? If yes, proceed to Step 3; if no, select an assay (preferably the one used by the institution's endocrine lab) and document it as the patient's standard assay.
STEP 3 — Classify or Stratify
Assess whether the upcoming test is for baseline evaluation, pre‑therapy, post‑therapy change, or routine monitoring. If the test evaluates response to a therapy change, schedule it 12 weeks after the change; if routine, follow the usual monitoring interval.
STEP 4 — Decide
Order the GH and IGF-1 assays using the patient's designated assay, ensuring the same laboratory and method are used for all serial measurements.
Clinical Guardrails / Mimics / Pitfalls
Do not switch assays between serial tests without documenting the change; avoid comparing GH or IGF-1 values across different assay platforms due to interassay variability; do not rely on a single random GH level for diagnosis or monitoring; ensure specimen handling (e.g., fasting, timing) is consistent for each draw.
Concrete Clinical Example
A 45‑year‑old woman with acromegaly on depot lanreotide has a prior IGF‑1 measured by a chemiluminescent assay at Lab X. Before increasing the lanreotide dose, the clinician confirms the prior assay, schedules IGF‑1 and GH draw 12 weeks post‑change, and orders both tests using the same chemiluminescent assay at Lab X to assess response.
Source: Acromegaly: An Endocrine Society Clinical Practice Guideline, Endocrine Society, 2014, https://doi.org/10.1210/jc.2014-2700