Endocrine Abstracts

Background: Harrington et al.¹ suggest that basal LH of ≥0.3 IU/l as measured by ICMA (Immulite 2500) has 100% specificity and 90.5% sensitivity in identifying progressive central precocious puberty (CPP).

Aims: To examine the utility of basal LH measured with the DELFIA assay for identifying CPP in girls.

Methods: All girls under age 9 years (median 7.3 years) investigated for precocious puberty with a GnRH test from 2010 to 2012 were studied retrospectively. The diagnosis of CPP was made by a consultant endocrinologist from reviewing follow-up clinical and growth data, ultrasound appearances of the uterus and ovaries, and biochemical results. Basal LH (IU/l) and results of the GnRH test were compared between girls diagnosed with and without CPP.

Results: Of the 77 girls, 21 were diagnosed with CPP having developed signs of precocious puberty at ≤8 years of age. Compared to girls without CPP, those with CPP had higher basal LH (median 0.5 vs 0.09, P<0.001), peak LH (13.0 vs 2.65, P<0.001), basal FSH (3.1 vs 1.2, P<0.001), and ratio of peak LH:FSH (1.1 vs 0.26, P<0.001). Peak FSH did not differ between the two groups (12.0 vs 9.9, P=0.2). As a cut-off for CPP, peak LH ≥5 IU/l gave 90.5% sensitivity and 82.1% specificity. A cut-off for basal LH of ≥0.3 IU/l gave 66.7% sensitivity and 91.1% specificity, suggesting lower sensitivity than the ICMA assay. Basal LH of ≥0.1 IU/l gave 85.7% sensitivity and 78.6% specificity.

Conclusion: Although basal LH alone may be useful as an initial screening test in identifying girls with CPP, the sensitivity and specificity for a cut-off of ≥0.3 IU/l varies according to the assay used. The limitations of assay-specific diagnostic cut-offs to differentiate girls with CPP from those without CPP need to be recognised.

Reference: 1. Harrington J et al. Arch. Dis. Child. 2014 99 15–20.