Comparison of two types of dipsticks to measure vaginal pH in clinical practice

To assess the practical use of two dispsticks for measuring vaginal pH with a range 4-7 (Merck and Macherey Nagel in the diagnosis of vaginal infections.

Routine gynaecological clinic in the General Hospital H Hart in Tienen and vulvo-vaginitis clinic in the University Hospital Gasthuisberg in Leuven, Belgium. After oral consent was obtained, 101 unselected consecutive women presenting for gynaecologic examination between 15 January 2004 and 15 February 2004 were included in an observational study. Vaginal smears were taken from the upper vaginal wall for pH measurement and for fresh wet mount examination by phase contrast microscopy for diagnosing lactobacillary grades and presence of pathogens. The observed color change of two different pH strips were compared with the color scale provided by the company by a junior investigator who was not familiar with the technique, nor with the pathology of the patient. The difficulty of the measurement was scored semi-quantitatively by assessing the time and effort necessary to decide on the correct pH.

Using the Macherey-Nagel method, the mean pH score was lower in women with normal flora and in women with vaginal infections than when the Merck method was used, but the difference was not significant. The pH became progressively more abnormal with increasing lactobacillary grades, a correlation that was similar for both tests. The reading of the pH sticks was significantly simpler and quicker with Macherey-Nagel than with Merck. Although difficult readings with Merck strips were four times more frequent in the group of women with abnormal flora than in women with normal flora, this difference was not significant.

(1) In both tests (Macherey-Nagel and Merck) the pH was more abnormal (higher) with increasing lactobacillary grades (declining number of lactobacillary morphotypes). (2) The Macherey-Nagel sticks are more user-friendly than Merck's.