Reproducibility And Predictive Value of First Voided Urinary LH vs. GnRH Stimulation Test In Girls with Premature- And Fast Puberty

Introduction: GnRH stimulation test is considered the gold standard for diagnosing premature puberty (PP). We previously found that first-voided urinary LH (FVU-LH) has better sensitivity and positive- and negative predictive value (PPV, NPV) than GnRH-stimulation in differentiating slowly- form rapidly-progressive PP. In this study we aimed to evaluate the reproducibility of FVU-LH. We also aimed to compare the predictive value of FVU-LH and GnRH-stimulation in diagnosing progressive puberty.

Methods: We have reviewed the medical records of all girls with premature- or fast-puberty that provided two consecutive FVU-LH samples, some of them simultaneously with GnRH stimulation test. Based on clinical and radiological data, progressive puberty was defined as skeletal age advancement >1 year and\or growth velocity > 2 SDS. The cutoff values for puberty were >5 IU/L and >1.16 IU/L for GnRH stimulation and FVU-LH, respectively.

Results: 114 FVU-LH pair tests were obtained and GnRH stimulation test was simultaneously performed in 49 cases. The low and high FVU-LH values were highly correlated (R=0.830; p<0.001). Only 23 pair tests (20%) were non-synchronized, namely, the FVU-LH values were on both sides of the cutoff (1.16 IU/L). The high FVU-LH values were best correlated with peak stimulated LH (R=0.674; p<0.001). High FVU-LH had better sensitivity (68% vs 39%) and NPV (33% vs 30%) than GnRH-stimulated peak LH, whereas peak LH had better specificity (91% vs 55%) and PPV (94% vs 84%) for predicting progressive puberty.

Conclusion: Double FVU-LH test can serve as a screening tool for PP and can save most GnRH stimulation tests.