ESPE Abstracts

Background: It remains unclear whether specimen pH can influence urinary LH and FSH assayed by immunochemiluminometric assays (ICMA).

Objective and hypotheses: To investigate the effect of specimen pH on urinary LH and FSH assayed by ICMA.

Method: The first morning-voided urine were collected and divided into 11 samples (each 100 ml). The urine pH was determined with a pH meter. Hydrochloric acid and sodium hydroxide were added to aliquots of urine as needed to achieve pH of 2.5, 3.5, 4.5, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, and 10.5 respectively. Each sample was then assayed for urinary LH and FSH respectively.

Results: Urinary LH at various pH as a percentage of urinary specimen at pH 7.5 (as same as pH in standard solution of LH or FSH) were as follows: 104% at pH 2.5, 109% at pH 3.5, 108% at pH 4.5, 105% at pH 5.5, 103% at pH 6.0, 100% at pH 6.5, 99% at pH 7.0, 99% at pH 8.0, 99% at pH 8.5, and 99% at pH 10.5; and for urinary FSH 14, 89, 95, 101, 102, 102, 99, 100, 99, and 95% respectively. Urinary LH were unaffected by changes of pH from 2.5 to 10.5, as well as urinary FSH from pH 3.5 to 10.5. But urinary FSH at pH 2.5 was lower than that at pH 7.5 (P=0.000).

Conclusion: ICMA can accurately measure urinary LH and FSH at a urinary physiological range of pH.