Our study revealed a strong correlation between the level of GtfB, as determined by ELISA using monoclonal antibodies, with the number of clinical lesions of our pediatric subjects. The ability to measure the level of a proven virulence factor and correlate it with clinical caries activity represents a step forward toward using the assay to aid in diagnosis of caries before overt lesions are present.
The failure to find a correlation between total Gtf activity and dmfs scores was surprising. It is possible that a significant amount of activity was removed when the saliva was clarified, through adsorption of enzymes to surfaces of bacteria [Vacca-Smith et al., 1996b
]. The activity assay measures both soluble and insoluble glucan formation [Schilling and Bowen, 1992
], whereas the ELISA as used here assesses individual enzymes [Yamashita et al., 1993
]. Further, it is possible that the assay measures Gtf activity from noncariogenic organisms and clearly does not distinguish different types of Gtf activity.
Our data confirmed previously reported correlations between salivary MS populations and dmfs [Alaluusua and Renkonen, 1983
; Köhler et al., 1988
; Berkowitz, 1996
; Mattos-Graner et al., 2000
]. The correlation between salivary GtfB and dmfs appears to be stronger, based on OR, than that between MS and dmfs. In an attempt to determine whether multiple salivary MS counts could provide better predictive power than a single assessment, Petti and Hausen [2000
] examined 304 initially caries-free 6-year-olds. The predictive power of a single test had a sensitivity of 29.1% and a specificity of 95.4%. Using multiple MS tests and comparing 0–1 positive tests with 2–3 positive tests, the sensitivity increased to 31.8% and the specificity to 97.6%. Several authors [Grindefjord et al., 1995
; van Palenstein et al., 2001
; Holbrook et al., 1993
] have used combinations of predictors including salivary MS to identify children at high risk to develop caries. Salivary MS counts contributed very little to identifying the at-risk groups. Using the Strip mutans chair side method to assess MS, the predictive ability varied in sensitivity 65% and specificity 86% in a low fluoride group to 40% (sensitivity) to 91% (specificity) in an optimum fluoride group. Our data are not strictly comparable because we carried out a cross-sectional study in young populations with contrasting levels of caries activity. Although the laboratory assessments were done blindly, cross-sectional studies have limitations.
We believe that using GtfB as a potential marker for caries activity has considerable advantages over cultural methods and other approaches such as PCR. GtfB is a proven virulence property of S. mutans
. Therefore, the test proposed here includes an agent directly involved in the pathogenesis of the disease. The test as envisaged could be used chair side and provide results within minutes. It is difficult to imagine primer and PCR mutans counts being used chair side, however carried out, as they require days to develop and need some laboratory equipment. In addition, as Bowden [1997
] pointed out, cultural methods do not differentiate among clonal types which may or may not be associated with virulence. This observation may also in part account for the relatively poor performance of MS counts as predictors of caries development. It may also explain why a correlation between MS counts and Gtf was not observed in this study (data not shown).
Data from a diverse range of different tests show a correlation with dmfs or DMFT in large populations, especially adults. For example, some tests determine the salivary and plaque populations of cariogenic micro-organisms such as lactobacilli and streptococci [Rogosa et al.,1951
; Duchin and van Houte, 1978
; Köhler and Bratthall, 1979
; Beighton, 1991
; Eisenberg et al., 1991
; Leverett et al., 1993a
]. Other methods have been used to identify aciduric and acidogenic organisms in saliva or in plaque, such as the Swab test and the Snyder test [Snyder, 1951
; Graingeret al.,1965
]. These tests are based on colorimetric measure of pH changes in culture media inoculated with either saliva or plaque samples. They appear to have little predictive value as applied to individuals and generally cannot be conducted at chair side.
Our data represent an essential first step in developing a simple and reliable caries activity and predictive test. The strong correlation between lesions and GtfB is certainly encouraging. A problem with our study and indeed all cross-sectional studies is that one has to assume that all clinical caries-free subjects are caries-inactive at the time of sampling. We have a strong suspicion that this was not necessarily so because 2 children who were considered caries-free but displayed high Gtf levels were found to have carious lesions 3–6 months after initial examination. Clearly, this difficulty could be obviated by a longitudinal study in similar populations. The sum of sensitivity and specificity should reach a value of 140 at least for high-risk prediction [Stamm et al., 1993
]. Our data show that the GtfB and CFU/milliliter MS met this value (152 vs. 167). Clearly, the true clinical value of our approach remains to be determined until the completion of a longitudinal study.
ECC constitutes a major public health problem and affects those who are least able to bear either the financial or health burden. Children in underserved areas visit a physician more readily than a dentist. If a simple test is developed, such as described here, it could be used by the physician to screen the children for caries risk during ‘well child’ visits and then make appropriate referrals of those identified as high risk to a dentist for the institution of preventive procedure, perhaps reducing the incidence of dental caries, obviating the need for extensive restorative care.