Agreement Between the 2- and 3-Step Methods for Identifying Subtle Menstrual Disturbances.
Level 3 - non-randomized controlled study
Observational diagnostic agreement study comparing two measurement protocols across 98 menstrual cycles.
PubMed 39043363 · doi:10.1123/ijspp.2024-0057
What was done
Researchers compared a simplified 2-step method (calendar tracking plus urinary ovulation testing) against the standard 3-step method (adding midluteal serum progesterone testing) for detecting subtle menstrual disturbances (SMDs). They evaluated 98 regular-length (21–35 days) menstrual cycles from 59 athletes. SMDs were defined as anovulation, short luteal phase (<10 days), or inadequate luteal phase (midluteal progesterone <16 nmol·L⁻¹). Agreement was assessed via Cohen kappa (κ) and the McNemar test.
What was found
Agreement between the two methods was substantial (κ = .72; 95% CI, .53–.91), but systematic bias was present (χ² = 5.14; P = .023). The 2-step method correctly identified 100% of cycles without an SMD, but detected only 61.1% of cycles with an SMD (95% CI, 51.4%–70.8%) confirmed by the 3-step method.
Why it matters
A positive result from the practical 2-step method reliably confirms a subtle menstrual disturbance, but a negative result cannot rule one out because it misses nearly 40% of affected cycles without blood sampling.
Limits
The sample size was modest (59 athletes, 98 cycles) and limited to regular-length cycles. Specific sports, training loads, and participant demographics were not detailed in the abstract.