Letters to the Editor
When the periodontal examination protocol for NHANES has been revised from partial-examination protocols (half-mouth examination of three sites per tooth) to full-mouth examination of six sites per tooth in order to improve the quality of prevalence data, the clinical examiners are required to put in more effort. In such a situation, other possible sources of error, such as the possibility of error related to the instrument, should be minimized by using periodontal probes that have markings at the level of each millimeter. A recent study has shown that the PCPUNC15 probe (which has markings at every millimeter from 1-15) tends to provide more exact periodontal measurements when compared to two other periodontal probes, one of which is the PCP2 periodontal probe.4 Holtfreter et al. also reported digit preference corresponding to the probe graduations while recording the periodontal measurements with different types of probes. The design of the PCPUNC15 probe accounts for greater reliability because it facilitates correct mathematical rounding of periodontal measurements and also reduces the opportunity for digit preference.4 Since prevalence data obtained from NHANES are widely used and cited, and attempts are being made to improve the quality of these prevalence data, we are of the opinion that, if possible, a more accurate probe such as PCPUNC15 should be employed for the periodontal examination in NHANES and other epidemiological studies in order to improve the validity of the data generated from such efforts. Pradeep S. Anand, Department of Periodontics, People’s College of Dental Sciences & Research Center, Bhopal, Madhya Pradesh State, India; Kavitha P. Kamath, Department of Oral Pathology, People’s Dental Academy, Bhopal, Madhya Pradesh State, India. The authors report no conflicts of interest related to this letter. REFERENCES 1. Eke PI, Page RC, Wei L, Thornton-Evans G, Genco RJ. Update of the case definitions for population-based surveillance of periodontitis. J Periodontol 2012;83: 1449-1454. 2. Eke PI, Dye BA, Wei L, Thornton-Evans GO, Genco RJ. Prevalence of periodontitis in adults in the United States: 2009 and 2010. J Dent Res 2012; 91:914-920. 3. Eke PI, Dye B. Assessment of self-report measures for predicting population prevalence of periodontitis. J Periodontol 2009;80:1371-1379. 4. Holtfreter B, Alte D, Schwahn C, Desvarieux M, Kocher T. Effects of different manual periodontal probes on periodontal measurements. J Clin Periodontol 2012;39:1032-1041. 766
Volume 85 • Number 6
Submitted August 31, 2013; accepted for publication October 14, 2013. doi: 10.1902/jop.2014.130543
Authors’ Response: The primary objective of the National Health and Nutrition Examination Survey (NHANES) is to collect surveillance data, i.e., prevalence and trend data, in the United States. For trend assessments, it is imperative that methodology remain consistent over time, and NHANES strives across all health components to ensure that the introduction of new methodology is justified and does not bias trend analyses. For this reason, the periodontal probe PCP2 (graduated at 2-mm intervals, i.e., 2, 4, 6, 8 mm) is used in NHANES and was the same type of probe used in 1988-1994, 1999-2004, and 2009+. Additionally, the recording procedures have not changed in the past 2 decades, and quality assurance performances are routinely reported.1 Periodontal measures from NHANES are widely used for surveillance and research.2 In this regard, very diverse case definitions for periodontitis are used, employing diverse cutoff values of single or combined periodontal measurements. Recently, the CDC Periodontal Disease Surveillance initiative suggested standard case definitions for periodontitis for use in surveillance to further standardize reporting of prevalence and trends. Definitions for three categories of periodontitis (i.e., mild, moderate, and severe) were provided based on attaining or exceeding different threshold cutoff values of probing depth (PD), attachment loss, or combinations of both measures from a full-mouth periodontal examination.3,4 The relative performance of these case definitions was initially tested in a convenience sample of US adults using the NHANES periodontal examination protocol.4 In their letter and example, Anand and Kamath suggest possible misclassification of CDC cases resulting from the current NHANES periodontal examination protocol. The authors are concerned that examiner error can occur because the PD cutoff values used in CDC case definitions do not correspond to depth marks on the PCP2 probes (e.g., 3 mm). To demonstrate their concern, the authors discuss possible errors arising when the gingival margin lies near the 3-mm level (i.e., approximately midway between the 2- and 4-mm depth markings on the PCP2 probe). Our response is to first note that the current NHANES procedure for probe measurements conservatively rounds down to the nearest millimeter, thus erring on the side of caution. Consequently, when the gingival margin lies below 3 mm but above 2 mm, the measure is rounded down
Letters to the Editor
J Periodontol • June 2014
as 2 mm. When the gingival margin is at the 3-mm marking (halfway between the 2- and 4-mm depth markings on the probe), the measurement is correctly recorded as 3 mm, and when the gingival margin lies above 3 mm (but below the 4-mm depth marking on the probe), the measure is correctly rounded down to 3 mm. Thus, this procedure correctly captures all sites with measures greater than or equal to 3 mm PD (‡3 mm PD). Therefore, a dichotomized case definition based on a cutoff value ‡3 mm will not be misclassified. This applies to all case definitions and measures of extent of periodontitis based on a fixed cutoff value and is the rationale for the common use of this approach with NHANES and other surveys using similar protocols. It is important to recognize that several factors including examiner clinical skills, probe design, and tissue conditions influence periodontal measurements within which priority consideration must be given to measurement factors that protect the integrity of prevalence and trends. It is impossible to optimally account for all possible sources of error including examiner error in large-scale surveillance of periodontitis. However, the inability to optimally account for all possible errors does not necessarily result in invalid measures or erroneous measurements. The validity of periodontal measures is relative to standard procedures of choice which, in turn, are influenced by multiple potential sources of error including examiner errors. It is for the data user to consider the protocol and possible biases resulting, and where necessary and available, to apply necessary correction factors to compensate for the effects of bias occurring in the survey. The current NHANES probe and recording procedures allow the survey to fulfill an important function of surveillance, i.e., to provide trend data over time. While changing the probe used in NHANES may improve the accuracy of periodontal measurements collected — thus marginally reducing the number of false-positives — it will also introduce new and significant bias that impacts trend analyses. In addition, the authors have not provided the necessary scientific evidence and evaluation for recommending that the current NHANES probe be changed and better served using the PCPUNC15. Specifically, in the
study by Holtfreter et al.5 referenced by Anand and Kamath, no statistically significant differences were reported between the PCPUNC15 and PCP2 probes for PD measures after controlling for all factors in multi-level modeling. Finally, as demonstrated above, the current NHANES procedure does not provide measures that compromise our ability to correctly classify cases based on the recommended cutoff values used for the CDC case definitions. Paul I. Eke, Division of Adult and Community Health, Centers for Disease Control and Prevention, Atlanta, GA; Roy C. Page, Regional Clinical Dental Research Center, School of Dentistry and Medicine, University of Washington, Seattle, WA; Liang Wei and Gina Thornton-Evans, Division of Oral Health, Centers for Disease Control and Prevention; Robert J. Genco, Schools of Dental Medicine and Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY. The authors report no conflicts of interest related to this letter. REFERENCES 1. Dye BA, Barker LK, Li X, Lewis BG, Beltran-Aguilar ED. Overview and quality assurance for the oral health component of the National Health and Nutrition Examination Survey (NHANES), 2005–2008. J Public Health Dent 2011;71:54-61. 2. Eke PI, Dye BA, Wei L, Thornton-Evans GO, Genco RJ. Prevalence of periodontitis in adults in the United States: 2009 and 2010. J Dent Res 2012;91:914-920. 3. Page R, Eke PI. Case definitions for use in populationbased surveillance of periodontitis. J Periodontol 2007; 78:1387-1399. 4. Eke PI, Page RC, Wei L, Thornton-Evans G, Genco RJ. Update of the case definitions for population-based surveillance of periodontitis. J Periodontol 2012;83: 1449-1454. 5. Holtfreter B, Alte D, Schwahn C, Desvarieux M, Kocher T. Effects of different manual periodontal probes on periodontal measurements. J Clin Periodontol 2012;39: 1032-1041. Submitted November 13, 2013; accepted for publication November 13, 2013. doi: 10.1902/jop.2014.130676
767
When the periodontal examination protocol for NHANES has been revised from partial-examination protocols (half-mouth examination of three sites per tooth) to full-mouth examination of six sites per tooth in order to improve the quality of prevalence data, the clinical examiners are required to put in more effort. In such a situation, other possible sources of error, such as the possibility of error related to the instrument, should be minimized by using periodontal probes that have markings at the level of each millimeter. A recent study has shown that the PCPUNC15 probe (which has markings at every millimeter from 1-15) tends to provide more exact periodontal measurements when compared to two other periodontal probes, one of which is the PCP2 periodontal probe.4 Holtfreter et al. also reported digit preference corresponding to the probe graduations while recording the periodontal measurements with different types of probes. The design of the PCPUNC15 probe accounts for greater reliability because it facilitates correct mathematical rounding of periodontal measurements and also reduces the opportunity for digit preference.4 Since prevalence data obtained from NHANES are widely used and cited, and attempts are being made to improve the quality of these prevalence data, we are of the opinion that, if possible, a more accurate probe such as PCPUNC15 should be employed for the periodontal examination in NHANES and other epidemiological studies in order to improve the validity of the data generated from such efforts. Pradeep S. Anand, Department of Periodontics, People’s College of Dental Sciences & Research Center, Bhopal, Madhya Pradesh State, India; Kavitha P. Kamath, Department of Oral Pathology, People’s Dental Academy, Bhopal, Madhya Pradesh State, India. The authors report no conflicts of interest related to this letter. REFERENCES 1. Eke PI, Page RC, Wei L, Thornton-Evans G, Genco RJ. Update of the case definitions for population-based surveillance of periodontitis. J Periodontol 2012;83: 1449-1454. 2. Eke PI, Dye BA, Wei L, Thornton-Evans GO, Genco RJ. Prevalence of periodontitis in adults in the United States: 2009 and 2010. J Dent Res 2012; 91:914-920. 3. Eke PI, Dye B. Assessment of self-report measures for predicting population prevalence of periodontitis. J Periodontol 2009;80:1371-1379. 4. Holtfreter B, Alte D, Schwahn C, Desvarieux M, Kocher T. Effects of different manual periodontal probes on periodontal measurements. J Clin Periodontol 2012;39:1032-1041. 766
Volume 85 • Number 6
Submitted August 31, 2013; accepted for publication October 14, 2013. doi: 10.1902/jop.2014.130543
Authors’ Response: The primary objective of the National Health and Nutrition Examination Survey (NHANES) is to collect surveillance data, i.e., prevalence and trend data, in the United States. For trend assessments, it is imperative that methodology remain consistent over time, and NHANES strives across all health components to ensure that the introduction of new methodology is justified and does not bias trend analyses. For this reason, the periodontal probe PCP2 (graduated at 2-mm intervals, i.e., 2, 4, 6, 8 mm) is used in NHANES and was the same type of probe used in 1988-1994, 1999-2004, and 2009+. Additionally, the recording procedures have not changed in the past 2 decades, and quality assurance performances are routinely reported.1 Periodontal measures from NHANES are widely used for surveillance and research.2 In this regard, very diverse case definitions for periodontitis are used, employing diverse cutoff values of single or combined periodontal measurements. Recently, the CDC Periodontal Disease Surveillance initiative suggested standard case definitions for periodontitis for use in surveillance to further standardize reporting of prevalence and trends. Definitions for three categories of periodontitis (i.e., mild, moderate, and severe) were provided based on attaining or exceeding different threshold cutoff values of probing depth (PD), attachment loss, or combinations of both measures from a full-mouth periodontal examination.3,4 The relative performance of these case definitions was initially tested in a convenience sample of US adults using the NHANES periodontal examination protocol.4 In their letter and example, Anand and Kamath suggest possible misclassification of CDC cases resulting from the current NHANES periodontal examination protocol. The authors are concerned that examiner error can occur because the PD cutoff values used in CDC case definitions do not correspond to depth marks on the PCP2 probes (e.g., 3 mm). To demonstrate their concern, the authors discuss possible errors arising when the gingival margin lies near the 3-mm level (i.e., approximately midway between the 2- and 4-mm depth markings on the PCP2 probe). Our response is to first note that the current NHANES procedure for probe measurements conservatively rounds down to the nearest millimeter, thus erring on the side of caution. Consequently, when the gingival margin lies below 3 mm but above 2 mm, the measure is rounded down
Letters to the Editor
J Periodontol • June 2014
as 2 mm. When the gingival margin is at the 3-mm marking (halfway between the 2- and 4-mm depth markings on the probe), the measurement is correctly recorded as 3 mm, and when the gingival margin lies above 3 mm (but below the 4-mm depth marking on the probe), the measure is correctly rounded down to 3 mm. Thus, this procedure correctly captures all sites with measures greater than or equal to 3 mm PD (‡3 mm PD). Therefore, a dichotomized case definition based on a cutoff value ‡3 mm will not be misclassified. This applies to all case definitions and measures of extent of periodontitis based on a fixed cutoff value and is the rationale for the common use of this approach with NHANES and other surveys using similar protocols. It is important to recognize that several factors including examiner clinical skills, probe design, and tissue conditions influence periodontal measurements within which priority consideration must be given to measurement factors that protect the integrity of prevalence and trends. It is impossible to optimally account for all possible sources of error including examiner error in large-scale surveillance of periodontitis. However, the inability to optimally account for all possible errors does not necessarily result in invalid measures or erroneous measurements. The validity of periodontal measures is relative to standard procedures of choice which, in turn, are influenced by multiple potential sources of error including examiner errors. It is for the data user to consider the protocol and possible biases resulting, and where necessary and available, to apply necessary correction factors to compensate for the effects of bias occurring in the survey. The current NHANES probe and recording procedures allow the survey to fulfill an important function of surveillance, i.e., to provide trend data over time. While changing the probe used in NHANES may improve the accuracy of periodontal measurements collected — thus marginally reducing the number of false-positives — it will also introduce new and significant bias that impacts trend analyses. In addition, the authors have not provided the necessary scientific evidence and evaluation for recommending that the current NHANES probe be changed and better served using the PCPUNC15. Specifically, in the
study by Holtfreter et al.5 referenced by Anand and Kamath, no statistically significant differences were reported between the PCPUNC15 and PCP2 probes for PD measures after controlling for all factors in multi-level modeling. Finally, as demonstrated above, the current NHANES procedure does not provide measures that compromise our ability to correctly classify cases based on the recommended cutoff values used for the CDC case definitions. Paul I. Eke, Division of Adult and Community Health, Centers for Disease Control and Prevention, Atlanta, GA; Roy C. Page, Regional Clinical Dental Research Center, School of Dentistry and Medicine, University of Washington, Seattle, WA; Liang Wei and Gina Thornton-Evans, Division of Oral Health, Centers for Disease Control and Prevention; Robert J. Genco, Schools of Dental Medicine and Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY. The authors report no conflicts of interest related to this letter. REFERENCES 1. Dye BA, Barker LK, Li X, Lewis BG, Beltran-Aguilar ED. Overview and quality assurance for the oral health component of the National Health and Nutrition Examination Survey (NHANES), 2005–2008. J Public Health Dent 2011;71:54-61. 2. Eke PI, Dye BA, Wei L, Thornton-Evans GO, Genco RJ. Prevalence of periodontitis in adults in the United States: 2009 and 2010. J Dent Res 2012;91:914-920. 3. Page R, Eke PI. Case definitions for use in populationbased surveillance of periodontitis. J Periodontol 2007; 78:1387-1399. 4. Eke PI, Page RC, Wei L, Thornton-Evans G, Genco RJ. Update of the case definitions for population-based surveillance of periodontitis. J Periodontol 2012;83: 1449-1454. 5. Holtfreter B, Alte D, Schwahn C, Desvarieux M, Kocher T. Effects of different manual periodontal probes on periodontal measurements. J Clin Periodontol 2012;39: 1032-1041. Submitted November 13, 2013; accepted for publication November 13, 2013. doi: 10.1902/jop.2014.130676
767
