Critical steps in electronic volume quantification of gingival crevicular fluid: the potential impact of evaporation, fluid retention, local conditions and repeated measurements

Abstract

Various methodological factors may operate during clinical gingival crevicular fluid (GCF) sampling, volume quantification or subsequent laboratory analysis. For precise volume quantification, specific concern for generation and maintenance of a reliable calibration curve, the potential risk of GCF loss as a result of evaporation or fluid retention on actual volume and the impact of local conditions is needed because each of these factors may act as a source of subsequent volumetric distortions. Thus, the present study aimed to analyse the impact of sample transfer time on the rate of evaporation and the possibility of fluid retention, and the impact of local conditions and number of replicated measurements on the reliability of calibration data. To analyse evaporative errors, standardized Periopaper strips provided with known test volumes (0.1 microl, 0.2 microl, 0.5 microl and 0.6 microl) were transferred to Periotron 8000 with different time intervals (immediately, 5 s, 30 s and 60 s). For fluid retention, after quantifying the actual volume of the strips provided with known volumes (0.1 microl and 0.6 microl) of two test fluids, a second set of measurements was performed using dry strips. To determine the impact of local conditions (temperature and humidity) and the validity of 3, 5 and 20 replications (0.0-0.6 microl with 0.1- microl increments) on device calibration for 20 degrees C and 25 degrees C, electronic readings were obtained from three devices at three different locations. Differences in volumetric data in each experimental design were statistically analysed. No significant fluid loss was observed within 5 s, but evaporation clearly led to volumetric distortions with extending transfer times (30 s or 60 s) (p < 0.05). Measurable amounts of fluid retention were found for both volumes and both test fluids, but not with identical patterns. Local conditions resulted in unique calibration data for each test volume and for each device. Although a 5 degrees C increase generally provided higher readings, this was not observed for all devices at all volumes. Additional replicates (n = 5 or n = 20) did not seem to add any further reliability to the triplicate scores for the given test volumes. The findings of the present study confirm the reliability of triplicate readings, and uniqueness of each device and electronic data and the distinct impact of local environmental conditions on the generation/maintenance of calibration scores for each particular device. Furthermore, they underline time-dependent evaporation and fluid retention as additional technical concerns and once again highlight the importance of methodological standardization of the electronic volume quantification process.