As I have mentioned in a previous post I had sent a letter to the editor of Journal of Dental Research, Professor W. Giannobile, in which I had asked the authors of a recent article on the periodontal findings of the 2009-2010 NHANES for some clarification regarding the quite confusing definition of attachment loss. There, Eke et al. (2012) wrote in the Material and Methods section,
“All periodontal examinations were conducted in a mobile examination center (MEC) by dental hygienists registered in at least one U.S. state. Gingival recession [= the distance between the free gingival margin (FGM) and the cemento-enamel junction (CEJ)] and pocket depth (PD) (= the distance from FGM to the bottom of the sulcus or periodontal pocket) were measured at 6 sites per tooth (mesio-, mid-, and disto-buccal; mesio-, mid-, and disto-lingual) for all teeth, excluding third molars. For measurements at each site, a periodontal probe (Hu-Friedy PVP 2TM, Chicago, IL, USA) with 2-, 4-, 6-, 8-, 10-, and 12-mm graduations was positioned parallel to the long axis of the tooth at each site. Data were recorded directly into an NHANES oral health data management program that instantly calculated attachment loss (AL) as the difference between probing depth and recession. Bleeding from probing and the presence of dental furcations were not assessed.” (Emphasis added.)
In my letter [pdf] I had pointed to (1) a possible glitch when calculating attachment loss as the difference, rather than the sum, between probing depth and recession; and (2) the fact that in the absence of any recession, periodontal probing depth must not automatically be regarded as attachment loss as the above description of the method suggested. I had provided a most trivial example regarding a 4 mm probing depth without recession which may be associated with either 0, 1, 2, 3, or 4 mm attachment loss, but it seems that the NHANES oral health data management program would have “instantly calculated” 4 mm. Then, (3) I had expressed my concern that either observation that attachment loss at certain thresholds was consistently higher than periodontal probing depth at respective thresholds in all age groups of the adult population of the United States, and the rather conspicuous finding that moderate periodontitis occurred at much higher prevalence than mild periodontal disease may in part be due to the apparently amended definition of attachment loss. And finally, as a constructive suggestion, (4) I asked the authors to compare the new 2009-2010 data with those of 1988-1994 by using the previous case definition (solely based on probing depth) by Albandar et al. (1999) in order to be able to “forget what I was told”, namely that prevalence, extent and severity of periodontal disease had in fact not decreased since NHANES III.
While Dr. Giannobile had informed me some time after I had sent my email that he would consider, after discussions with the authors, either an Erratum or publishing my letter accompanied by a respective authors’ response, I have received yesterday the requested clarification by the authors who write,
“The algorithm used to calculate attachment loss (AL) in NHANES can intuitively be misunderstood because it is stated that subtraction measures of gingival recession from measures of pocket depth PD (and not added as one would expect intuitively). However, mathematically this is correct. The recession is called out as a negative number by the examiner and is subtracted from the PD i.e., PD – (-recession) = PD + recession (if the FGM is below the CEJ) which adds up to the sum of the recession plus the PD. If the FGM is above the CEJ, then it is the direct sum of the recession (which is positive) and PD. Thus in NHANES, AL is calculated from three anatomical points versus a direct measure from the CEJ to the bottom of the pocket as may be done clinically (Clinical attachment loss). There is a long history behind why NCHS has used this approach, however this is how AL has been determined for all previous NHANES including NHANES III (the dataset used by Albandar 1999), NHANES 1999-2004 and NHANES 2009 – 2010.”
Dr. Giannobile “regret[s] to inform [me] that we are declining it for publication as a letter or erratum.”
The description of how attachment loss had been calculated is now very similar to the way it was described by Albandar et al. (1999) who wrote,
“The distance from the cemento-enamel junction (CEJ) to the free gingival margin (FGM) and the distance from the FGM to the bottom of the pocket/sulcus were assessed at the mesio-buccal and mid-buccal surfaces. The measurements were made in millimeters and were rounded to the lowest whole millimeter. The assessment was made by using the NIDR periodontal probe. The probing depth was defined as the FGM/sulcus measurement. The CEJ/FGM distance was given a negative sign if the gingival margin was located on the root. Attachment loss was defined as the distance from CEJ to the bottom of the pocket/sulcus and was calculated as the difference between CEJ/FGM and FGM/sulcus distances (or the sum of the 2 distances if FGM was on the root).”
In my letter to Dr. Giannobile, I had compared the definitions by Eke et al. (2012) and Albandar et al. (1999) and had to conclude that they basically differ. Albandar et al. (1999) outline an overly complicated albeit correct way avoiding the term “recession” at all. The introduction of “recession” (from Latin recessus, i.e., “retreat”) by Eke et al. (2012) is problematic when it comes to the fact that it has to get a minus sign if the cemento-enamel junction is located below the gingival margin. Anyway, if that is so, this should be mentioned in Material and Methods.
If the ways how attachment loss had been measured in NHANES III (Albandar et al. 1999) and 2009-2010 NHANES were in fact identical, an Erratum to the paper by Eke et al. (2012) would be desirable. In future surveys, a correct reference to Albandar et al. (1999) would suffice.
What still remains is the suggested comparison of prevalence of mild, moderate and advanced periodontitis using case definitions (based on periodontal probing depth and furcation involvement, not attachment loss) by Albandar et al. (1999). Since furcation involvement had not been assessed by Eke et al. (2012), that might not even be possible here.
5 January 2013 @ 10:03 am.
Last modified January 6, 2013.