Accurate measurement of female genital tract fluid dilution in cervicovaginal lavage samples

Abstract

An ion chromatographic method with conductivity detection for the precise and accurate analysis of lithium ions in phosphate-buffered saline, used as a cervicovaginal lavage (CVL) fluid, was developed and validated. The lithium ion dilution factor during the CVL is used to calculate the volume of cervicovaginal fluid (CVF) collected. Initial CVL Li+ concentrations of 1 mM and 10 mM were evaluated. The method is robust, practical, and afforded an accurate measurement (5% of the measurement, or better) at 24 μL of vaginal fluid simulant collected per mL of CVL fluid, as low as 5 μL mL−1 using 10 mM Li+ with a measurement accuracy of 6.7%. Ion chromatograms of real-world CVL samples collected in vivo from common animal models (sheep and pig-tailed macaque) and a human volunteer demonstrate that the analysis is interference-free. The method is readily transferrable and should enable the accurate measurement of CVF volume collected during CVLs benefitting a broad range of research disciplines, including pharmacokinetic, pharmacodynamic, metabolomic, and microbiome studies.

Combination Pod-Intravaginal Ring Delivers Antiretroviral Agents for HIV Prophylaxis: Pharmacokinetic Evaluation in an Ovine Model

“…The vaginal fluid volume collected during the CVL as an additive in the naive CVL fluid was measured by ion chromatography (IC) and calculated using LiCl (1 mM) according to methods discussed in detail elsewhere (34).…”

“…This uncertainty can lead to large errors in the calculation of CVF drug concentrations from CVL fluid measurements, confounding the interpretation of results. We have developed a novel method for quantifying the amount of CVF collected by CVL that uses IC to precisely and accurately measure the dilution of Li ϩ added to the CVL fluid (34) and used this method for the first time to determine the CVF volume collected in a preclinical in vivo PK study. A sensitive LC-MS/MS assay for TFV-DP, the pharmacologically active metabolite of TFV, in vaginal tissue homogenate was extended to sheep and used to provide the first measure (Fig.…”

Evaluation of the Pig-Tailed Macaque (Macaca nemestrina) as a Model of Human Staphylococcus aureus Nasal Carriage

“…Considering the experimental limitations that exist in studying SANC in humans, paired with the lack of a reproducible human-relevant model, we sought to determine whether pig-tailed macaques (Macaca nemestrina) are natural carriers of S. aureus, whether they may be experimentally colonized with S. aureus strains relevant to human S. aureus carriage, and whether their innate response to S. aureus models the human response. Macaca nemestrina pig-tailed macaques have previously been shown to be able to be used as a model of the human condition for airway development, immune function, hormonal regulation, and microbiome complexity (22)(23)(24)(25)(26). Here, we screened 17 pig-tailed macaques living in the Washington National Primate Research Center (WaNPRC) for nasal or pharyngeal S. aureus, and 14 were nasal S. aureus positive at one or both screening sessions (8 weeks apart).…”

Safety and pharmacokinetics of single, dual, and triple antiretroviral drug formulations delivered by pod-intravaginal rings designed for HIV-1 prevention: A Phase I trial

“…The measurement of Li + , an exogenous tracer added to the naïve CVL fluid, was used to correct the CVL drug concentration analyses for dilution in the TDF-FTC-MVC pod-IVR group and, hence, affords the corresponding drug concentrations in undiluted CVF [ 37 ]. The corrected CVL drug concentrations exhibited a moderate (total TFV and MVC) to weak (FTC) correlation with paired CVF (Dacron swab) drug concentrations ( S4 Fig ): TFV (total TFV, reported as the molar sum of TDF and TFV concentrations); slope, 7.53 ± 0.84; R 2 , 0.889; FTC; slope, 2.40 ± 1.43; R 2 , 0.220; MVC; slope, 4.37 ± 1.11; R 2 , 0.609.…”

“…CVLs were performed by instilling a sterile phosphate-buffered saline solution (2.5 mL) containing LiCl (1 mM). The added LiCl allowed dilution of the collected CVF to be calculated in the TDF-FTC-MVC group using an established method [ 37 ]. CVL samples were not compensated for dilution in the TDF and TDF-FTC groups.…”