Methodological considerations in the assessment of gingival crevicular fluid volume

In 4 studies on gingival crevicular fluid volume (GCFV) determination, the reliability of measurements, influences of plaque, circadian rhythms and stability over 24 h were examined. Samples were taken at 2 sites with a modified intracrevicular method. Reliability (n=40): repeated GCFV determinations within 5 min revealed good reliability coefficients (r(tt)>0.80). Influences of supragingival plaque (n=80): repeated GCFV determinations within 5 min with plaque removal between measurements in fourty subjects, the other subjects serving as control, revealed no group differences with respect to the differences between measurements. Circadian rhythms (n=20): GCFV was assessed 6x throughout the day. Repeated measures ANOVA revealed no significant time effect. Stability over 24 h under constant clinical conditions (n=20): measures were taken at 16:00 h on 2 consecutive days, several disturbing variables were kept constant. Retest correlations revealed a low stability (i.e., high variability) of GCFV measures under constant clinical conditions (r(tt)=0.38 for tooth 11 and r(tt)= -0.25 for tooth 26). It is concluded that GCFV determination can be done with high reliability, the validity of measurements neither being affected by supragingival plaque nor by diurnal rhythms. The low stability of measurements questions the validity of GCFV for diagnostic purposes.