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PubMed1978

The use of simple image analysers in lung morphometry.

We have used several commercially available image analysers to measure the inter-alveolar wall distance on histologic sections of animal and human lungs. Inter- and intra-observer variations using these machines are small, and very similar results are obtained using different machines. The recorded result depends on the magnification used since higher resolution produces more intercepts. The plane in which the measurement is made affects the result, representing the difference in shrinkage from fixed tissue to stained slides in the horizontal and vertical planes. Machine-measured inter-alveolar wall distances are smaller than those measured by humans because of the spurious intercepts made by the image analysers. However, the measurements are highly correlated and human-measured inter-alveolar wall distances can be closely predicted from the machine-measured ones. The number of alveoli per unit volume is less well predicted from the average inter-alveolar wall distance. Image analysers may possibly play a useful role in making similar simple measurements in other organs.

Animals↗
PubMed1986

Stereology for anisotropic cells: application to growth cartilage.

A number of either new or recently available stereological methods are described for estimating volume, surface area and number of anisotropic cells. The methods are illustrated with direct reference to the epiphyseal growth plate. Different estimates of a given quantity are obtained by applying alternative methods to the same set of sections, in order to compare the relative merits of the methods. For instance, the surface area of the cells is estimated via the Dimroth-Watson model (which gives a measure of the degree of anisotropy in addition to the surface area estimate) and from vertical sections using cycloid test systems. Cell number is estimated by traditional unfolding methods and by the new disector method. Also, volume-weighted mean cell volume is estimated from vertical sections via point-sampled intercepts using two different kinds of rulers to classify intercept lengths. Finally, nested design statistics is applied to a set of data from twelve animals in order to compare the relative impacts of biological and stereological (sampling) variations on the observed coefficient of error of a group mean estimate. The preferred methods are listed in the final section.

Animals↗
PubMed1990

Estimating mean particle volume and number from random sections by sampling profile boundaries.

We describe some new shape-independent stereological estimates of particle mean volume and surface area. Finding volumes or surface areas of cell nuclei, from electron micrographs of random thin sections, is a central problem of biological stereology. The well-known point-sampled intercept (PSI) method samples profile interiors to find the volume-weighted mean volume. This can be used in place of the true mean volume, but to do so introduces bias when volumes vary a great deal, as they do in fixed specimens. Jensen and Gundersen quite recently extended the PSI estimator to provide particle surface area, with no bias in the case of uniform surface areas. Here we extend the PSI volume estimator in a different way, sampling profile boundaries rather than their interiors. We obtain a boundary-sampled intercept (BSI) volume estimator, simpler than the PSI surface area estimator, but also unbiased for uniform surface areas. Both of these estimators are attractive, for example, in measuring and counting cell nuclei, where membrane surface area varies less than volume. Furthermore, they have no shape bias whatsoever. This paper also examines the general relationship between boundary- and area-sampled estimates, and we clarify the formal connection between our volume estimator and the PSI surface area estimator. We also calculate and compare their theoretical efficiencies.

Cell Nucleus↗
PubMed1987

Allergy indices based on allergen dose-response curve in a randomly selected sample of schoolchildren.

Skin-test sensitivity was computed in 61 schoolchildren drawn from a stratified random sample in order to generate two allergy indices based on a quantitative skin-test assay: Individual Allergy Index (IAI) and Population Allergy Index (PAI). The former to quantitate IgE-mediated skin test sensitivity of each subject, the latter to describe the degree of skin reactivity of our sample to a single allergen. Five allergen extracts were tested at 4-fold dilutions. Sensitivity endpoint data were used to generate IAI. Frequency distribution of IAI seemed to be bimodal as asymptomatic subjects gathered at the lower part while symptomatic children showed a peak in the middle. By means of criteria based on the relation between IAI and the prevalence of symptoms we were able to classify atopy in five classes from normal (all asymptomatic subjects) to severe atopy (all symptomatic subjects). Each positive reaction was plotted as a function of the allergen concentration eliciting the weal, and linear regression with confidence limits was calculated for grass and Dermatophagoides pteronyssinus only. PAI was represented by the slope, which depends on the reactivity of the sample, and the intercept, which involves the potency of the allergen as well. Grass and D. pteronyssinus showed the same slope while the intercepts differed. The slope increased if we considered symptomatic subjects only. We propose both these indices for clinical and epidemiological studies.

Adolescent↗
PubMed1984

Amino acid sequence diversity between bovine epidermal cytokeratin polypeptides of the basic (type II) subfamily as determined from cDNA clones.

The nucleotide sequences of four cDNA clones, each representing the carboxyterminal portion of a bovine epidermal cytokeratin of the "basic" (type II) subfamily, were determined, i.e., components Ia (Mr 68,000), Ib (Mr 68,000), III (Mr 60,000), and IV (Mr 59,000). The comparison of the sequences with each other and with the human type-II cytokeratin of Mr 56,000 reported by Hanukoglu and Fuchs [24] allows the following conclusions: The four major epidermal keratins of the basic (type II) subfamily, which are co-expressed in keratinocytes of the bovine muzzle, exhibit a high homology (greater than 90%) in the alpha-helical portion, but differ considerably in their nonhelical carboxy-terminal regions. The nonhelical carboxyterminal regions of all four cytokeratins are exceptionally rich in glycine and serine. Within the extrahelical tail, three different domains can be distinguished. The consensus sequence TYR(X)LLEGE which demarcates the end of the alpha-helical rod in all intermediate filaments is followed by a relatively short (22-27 amino acids) intercept rich in hydroxy amino acids and valine (carboxyterminal tail domain C1). This is followed by a long region that is variable in size and sequence, rich in glycine di-, tri-, and tetrapeptides, and contains diverse repeated sequences (domain C2). This is followed by another short (20 residues) hydroxy-amino-acid-rich intercept (domain C3) that ends with a conspicuously basic sequence of approximately four to six carboxyterminal amino acids. The first half of domain C1 is also homologous in all four keratins, suggesting that this region also assumes a common conformation and/or serves a special common function.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1975

Prostaglandin 15-hydroxy dehydrogenase from human placenta.

The enzyme system prostaglandin 15-hydroxy dehydrogenase, which catalyzes the inactivation of all biologically active prostaglandins, has been purified 1270-fold from human placenta. Kinetic studies on the enzyme have provided information on a well-organized control mechanism to avoid prostaglandin accumulation and for a fast prostaglandin degradation. 15-Ketoprostaglandin E2 and 13,14-dihydro-15-ketoprostaglandin E2 inhibit prostaglandin 15-hydroxy dehydrogenase non-competitively with respect to prostaglandin E2. The rate equation of enzyme reaction for two substrates was used for determination of the equilibrium constant and Michaelis constants of the enzyme. The following kinetic constants for prostaglandin 15-hydroxy dehydrogenase have been found. The equilibrium constant with repect to prostaglandin E2 is 18 muM, the Michaelis constant Km for prostaglandin E2 is 1 muM for NAD+ 44muM. The inhibition constants for 15-ketoprostaglandin E2 ar Ki(slope) = 70 muM, Ki(intercept) = 150 muM, and for 13,14-dihydro-15-ketoprostaglandin E2 Ki(slope) = 80 muM, and Ki(intercept) = 150 muM. The maximal velocity for the forward reaction is V1 = 0.45 mumol/min. These kinetic data exclude a random or ping-pong mechanism, and also a Theorell-Chance type as suggested by Braithwaite and Jarabak. We propose, therefore, a sequential ordered mechanism. The isoelectric point for prostaglandin 15-hydroxy dehydrogenase is at pH 5.35, judged by isoelectric focusing.

Alcohol Oxidoreductases↗
PubMed1996

Rationalization of the strength of metal binding to human serum transferrin.

A wide range of metal ions of natural, therapeutic, diagnostic and toxic interest are transported by serum transferrin (80 kDa). It is therefore important to understand the factors that control the strength of metal binding. We show here that even though Sc3+ has only slightly larger ionic radius than Fe3+ (0.075 nm versus 0.065 nm), it binds to the C-lobe and N-lobe sites much more weakly: logK1* (bicarbonate-independent binding constant) 14.6 +/- 0.2, logK2* 13.3 +/- 0.3, respectively (10 mM Hepes, 5 mM bicarbonate, 310 K). Preferential binding to the C-lobe was established by 1H-NMR spectroscopy. We show that the strength of binding of divalent and trivalent metal ions to human serum transferrin correlates with metal ion acidity [and therefore with the strength of binding to hydroxide, K1(OH)]. The correlations are of predictive value for a range of other metal ions. The plot of logK1* (human serum transferrin) versus logK1(OH) has a negative intercept consistent with unfavorable entropy effects due to lobe closure of apotransferrin on binding of metal ions. This interpretation was tested by comparison with similar correlations of the strength of metal binding to the enzymes carbonic anhydrase and carboxypeptidase with that for the low-M(r) ligand imidazole. These plots have positive intercepts consistent with the preorganized (entatic) state of these metalloenzymes (favorable entropy effects on metal binding).

Binding Sites↗
PubMed1996

Recovery of high speed memory scanning after transient global amnesia: a case report.

We described the case of a 59 year old female with transient global amnesia (TGA) who had been examined neuropsychologically using Sternberg's paradigm and a random number generation (RNG) task on the following day, 1 week and 4 weeks after a TGA episode. The slope value of the linear function, a measure of cognitive memory scanning speed, decreased with time and showed a marked decrease 1 week after TGA, suggesting that the stage of serial and exhaustive scanning recovered within 1 week. The zero-intercept value, on the other hand, increased during 1 week but decreased 4 weeks later and was not related directly to recovery from TGA. The performance in RNG task improved 1 week later, but deteriorated 4 weeks after the episode. Such a change in RNG was in accordance with that of the zero-intercept value, predicting a relationship. It is concluded that the subclinical memory deficit, detected with these tasks, persisted longer than clinical recovery from TGA.

Amnesia↗
PubMed1989

What do statistics really tell us about the quality of the data from self-monitoring of blood glucose?

Recently a number of studies have examined the quality of the data obtained from various systems used in the self-monitoring of blood glucose. Many of these studies have used parametric statistical techniques such as the Pearson product-moment correlation (r) and linear regression to evaluate the errors associated with self-monitoring results. These statistical methods, while well known and easily computed on modern computers, are often inappropriate for evaluating either the amount of error associated with self-monitoring or the clinical significance of these errors. For example: 1. a correlation of 1.00 does not necessarily mean that the measurements from a self-monitoring system agree with the true values and are without error; 2. a correlation close to 0.00 does not necessarily mean that the measurements from self-monitoring differ widely from the true values and possess large amounts of error; 3. a slope of 1.0 and a y-intercept of 0.0 in a linear regression equation do not necessarily mean that the self-monitoring measurements agree with the true values; 4. a slope and y-intercept that deviate significantly from 1.0 and 0.0, respectively, do not necessarily mean that such measurements differ widely from the true values. The present paper illustrates some of the limitations and common misconceptions concerning these statistics, and shows that a reliance on these techniques alone can, in certain circumstances, lead to misleading estimates of the amount of error associated with self-monitoring systems and inappropriate descriptions of the clinical significance of these errors.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Glucose Self-Monitoring↗
PubMed2000

An endogenous circadian rhythm of respiratory control in humans.

Many physiological and behavioural functions have circadian rhythms - endogenous oscillations with a period of approximately 24 h that can occur even in the absence of sleep. We determined whether there is an endogenous circadian rhythm in breathing, metabolism and ventilatory chemosensitivity in humans. Ten healthy, adult males were studied throughout 4 days in a stable laboratory environment. After two initial baseline days (16 h wakefulness plus 8 h sleep) that served to achieve a steady state, subjects were studied under constant behavioural and environmental conditions throughout 41 h of wakefulness. Ventilation, metabolism and the magnitude of the hypercapnic ventilatory response (HCVR) were measured every 2 h. Individuals' data were aligned according to circadian phase (core body temperature minimum; CBTmin) and averaged. In the group average data, there was a significant and large amplitude circadian variation in HCVR slope (average of +/-0.4 l min-1 mmHg-1; corresponding to +/-12.1 % of 24 h mean), and a smaller amplitude rhythm in the HCVR x-axis intercept (average of +/-1.1 mmHg; +/-2.1 % of 24 h mean). Despite a significant circadian variation in metabolism (+/-3.2 % of 24 h mean), there were no detectable rhythms in tidal volume, respiratory frequency or ventilation. This small discrepancy between metabolism and ventilation led to a small but significant circadian variation in end-tidal PCO2 (PET,CO2; +/-0.6 mmHg; +/-1.5 % of 24 h mean). The circadian minima of the group-averaged respiratory variables occurred 6-8 h earlier than CBTmin, suggesting that endogenous changes in CBT across the circadian cycle have less of an effect on respiration than equivalent experimentally induced changes in CBT. Throughout these circadian changes, there were no correlations between HCVR parameters (slope or x-axis intercept) and either resting ventilation or resting PET,CO2. This suggests that ventilation and PET,CO2 are little influenced by central chemosensory respiratory control in awake humans even when at rest under constant environmental and behavioural conditions. The characteristic change in PET,CO2 during non-rapid eye movement sleep was shown to be independent of circadian variations in PET,CO2, and probably reflects a change from predominantly behavioural to predominantly chemosensory respiratory control. This study has documented the existence and magnitude of circadian variations in respiration and respiratory control in awake humans for the first time under constant behavioural and environmental conditions. These results provide unique insights into respiratory control in awake humans, and highlight the importance of considering the phase of the circadian cycle in studies of respiratory control.

Adult↗
PubMed1984

Total body bone mineral in vivo by dual photon absorptiometry. II. Accuracy.

We investigated the accuracy of total body mineral (TBBM) measured by dual photon absorptiometry (1 Ci 153Gd source, 44 and 100 KeV) using skeletons, soft tissue equivalent materials and whole cadaver extremities. The accuracy was assessed on five skeletons (r = 0.99, SEE = 1.5%). The influence of the soft tissue composition on the TBBM measurement was investigated in the same five skeletons. They were scanned in a 16 cm thickness of ethanol solutions of different concentration (0, 20, 40, 60, 80, 100% ethanol) and only a 2% difference (non-significant) was found between measuring 100% ethanol and 100% water. Furthermore, seven whole cadaver extremities were scanned before and after removal of the soft tissues (r = 0.995, SEE = 6.3%). The slope was not different from one and the intercept not different from zero. Equipment at the University of Wisconsin, Madison, and at Glostrup Hospital, Denmark, was compared by measuring the same healthy subjects and skeletons on both scanners. The Glostrup and Madison TBBM values correlated well (r = 0.99, SEE = 5.8%) and the intercept (345 Glostrup arbitrary units) was not significantly different from zero (P greater than 0.05). The TBBM results were calibrated into total body calcium (TBCa) and no significant difference was found between Glostrup and Madison TBCa values (P greater than 0.20).

Bone and Bones↗
PubMed1999

A new method for rapid measurement of lactate in fetal and neonatal blood.

A prospective trial to determine the accuracy and precision of the Boehringer Mannheim Accusport handheld lactate meter in measuring plasma lactate levels in umbilical cord blood and neonatal blood microsamples was performed in the labour ward and the neonatal intensive care unit of the NepeanHospital. Specimens were collected from the umbilical artery of 160 consecutive deliveries covering gestations from 26 to 42 weeks, and from 110 umbilical artery catheters covering a range of gestations from 26 to 41 weeks. Serum was also obtained from an exchange transfusion for coefficient of variation analysis. Blood was simultaneously tested for lactic acid concentration on the Boehringer Mannheim (BM) Accusport held lactate meter and the Radiometer ABL 625 blood-gas machine. Clinical data from the mother and baby were recorded together with the full blood-gas analysis for comparison with the lactate measures. Coefficients of variation for the BM Accusport lactate meter were established by a further 120 samples of plasma lactate at 6 concentrations from 1 to 20 mmol/L. The stability of measurements with the BM lactate meter over a wide range of temperatures was ascertained by repeated sampling of known concentrations of plasma lactate from 0.5 degrees C to 37 degrees C. The BM Accusport lactate meter was found to be accurate from 1 mmol/L to 20 mmol/L with a Passing Bablok regression line y = 0.004 + 0.915 x (95% CI of slope of 0.889 to 0.946 and intercept -0.138 to 0.094) for whole blood, and y = 0.200 + 1.000 x (95% CI of slope 0.989 to 1.018 and intercept 0.080 to 0.222) for plasma. Between run coefficient of variation (CV) was calculated to be 1.23% to 5.53% over the clinically significant range (2.2-19.3 mmol/L). The BM lactate meter was accurate from 5 to 37 degrees C. At 0.5 degrees C the BM lactate meter significantly underestimated the plasma lactate concentration. There was no significant effect of haematocrit (41.5 to 62%), gestation, or operator on the accuracy of the BM lactate meter. The Accusport handheld lactate meter is an accurate, commercially available, method of measuring plasma lactate levels in only 60 seconds at the point-of-care. It requires only 15 microL of blood and is significantly cheaper than other assay methods. The BM lactate meter is well suited to assess lactic acidaemia of fetal scalp and neonatal blood samples to help quantify hypoxic stress in the perinatal period.

Blood Chemical Analysis↗
PubMed2005

Evolving concepts in the quantitative analysis of the determinants of the plasma water sodium concentration and the pathophysiology and treatment of the dysnatremias.

The physiologic and clinical implications of the empirical formula originally discovered by Edelman et al [J Clin Invest 37:1236-1256, 1958] relating the plasma water sodium concentration ([Na(+)](pw)) to the total exchangeable sodium (Na(e)), total exchangeable potassium (K(e)), and total body water (TBW) have recently been elucidated. It is quite remarkable that the full significance of the Edelman equation discovered almost 50 years ago had remained unrecognized by clinicians and physiologists until recently. Although Edelman and colleagues had shown that the [Na(+)](pw) is proportional to the magnitude of (Na(e)+ K(e))/TBW, the linear equation relating [Na(+)](pw) to (Na(e)+ K(e))/TBW had a slope greater than unity of 1.11, and a non-zero y intercept of -25.6 whose significance was unrecognized and more often than not ignored. It has recently been demonstrated that the slope and y intercept in this equation are quantitatively determined by several additional physiologic parameters, which in addition to (Na(e)+ K(e))/TBW, play a role both in modulating the [Na(+)](pw) and in the generation of the dysnatremias. Even more remarkably, based only on the theoretical principles of Gibbs-Donnan and osmotic equilibrium, all the physiologic parameters that determine the magnitude of the [Na(+)](pw) can be incorporated into a simple conceptual and mathematical framework that sheds light on a broad of range of seemingly unrelated topics that have heretofore been treated separately clinically, including (1) effect of changes in the mass balance of Na(+), K(+), and H(2)O on the [Na(+)](pw); (2) modulation of [Na(+)](pw) in hyperglycemic states; (3) definition of an isonatric solution; (4) current formulas used to quantitate electrolyte-free water excretion; (5) complex role of K(+) in modulating the [Na(+)](pw); and (6) quantitative analysis of the generation and treatment of the dysnatremias. Moreover, this analysis has also proven to be an indispensable tool for deriving new formulas to aid the clinician in both interpreting the pathogenesis and treating the dysnatremias.

Humans↗
PubMed2004

Functional characteristics of buffy-coat PLTs photochemically treated with amotosalen-HCl for pathogen inactivation.

BACKGROUND: One blood system for PLTs (INTERCEPT, Baxter Transfusion Therapies) is based on photochemical treatment (PCT) with small molecules that target cross-link nucleic acids (Helinx technology, Cerus Corp.) with amotosalen-HCl (S-59) and UVA light (320-400 nm) to inactivate pathogens and WBCs. STUDY DESIGN AND METHODS: A two-arm in vitro study was conducted to compare pooled buffy-coat-derived PLT concentrates (PCs) treated with the INTERCEPT blood system, resuspended in PLT additive solution (PAS) III (InterSol, Baxter Transfusion Therapies), and stored for up to 7 days (test units, n = 20) with unpaired, nontreated PCs, resuspended in PAS II (T-Sol, Baxter Transfusion Therapies), and prepared at the same center in the same manner (control units, n = 18). RESULTS: PLT dose (x 1011/unit +/- SD) on Day 1 immediately following PCT was 3.0 +/- 0.4 for test units and 3.2 +/- 0.4 for control units. After 7 days of storage, the pH of all test units was maintained above 6.8. No marked trend was observed in the hypotonic shock response (HSR). Values among study groups were similar at the end of observation period: 68 +/- 11 percent for control unites versus 67 +/- 8 percent for test units (p > 0.05). Aggregation response to ristocetin was slightly lower in test units: at Day 7, 65 +/- 10 percent versus 76 +/- 6 percent (p < 0.05). Significantly higher (p < 0.001) glucose consumption, lactate production, and CD62P expression were observed in test units. CONCLUSION: Compared to nontreated PLTs, the PCT process was associated with a variety of differences of in vitro analyses. Although significant, these changes were relatively small in most cases. Characteristics correlated with survival in vivo such as HSR and swirling were comparable between both study groups, indicating that the viability of the majority of cells appears to have persisted throughout 7 days of storage. The impact of this finding, however, remains to be investigated in clinical trials performed with 7-day stored PLTs.

Bacterial Infections↗
PubMed1997

Categorical regression analysis of acute exposure to tetrachloroethylene.

Exposure-response analysis of acute noncancer risks should consider both concentration (C) and duration (T) of exposure, as well as severity of response. Stratified categorical regression is a form of meta-analysis that addresses these needs by combining studies and analyzing response data expressed as ordinal severity categories. A generalized linear model for ordinal data was used to estimate the probability of response associated with exposure and severity category. Stratification of the regression model addresses systematic differences among studies by allowing one or more model parameters to vary across strata defined, for example, by species and sex. The ability to treat partial information addresses the difficulties in assigning consistent severity scores. Studies containing information on acute effects of tetrachloroethylene in rats, mice, and humans were analyzed. The mouse data were highly uncertain due to lack of data on effects of low concentrations and were excluded from the analysis. A model with species-specific concentration intercept terms for rat and human central nervous system data improved fit to the data compared with the base model (combined species). More complex models with strata defined by sex and species did not improve the fit. The stratified regression model allows human effect levels to be identified more confidently by basing the intercept on human data and the slope parameters on the combined data (on a C x T plot). This analysis provides an exposure-response function for acute exposures to tetrachloroethylene using categorical regression analysis.

Administration, Inhalation↗
PubMed2006

Estimating and comparing the distribution of onset of disease from prevalence case-control data.

Age at ascertainment from prevalence case-control data identifies the age-specific odds of disease. When age at onset is available from the cases, the conditional distribution of age at onset, given that disease occurs, is identifiable. Combining both kinds of information by introducing a multiplicative intercept allows identification of the marginal distribution of age at onset. Here, the approach is extended to the two-sample setting through a generalization of the multiplicative intercept model. The efficiency of the approach is explored and a test statistic based on the integrated difference between distribution function estimates is proposed. An approach to regularization of the likelihood is discussed. The methods are illustrated through an application to data on colorectal polyps obtained from a case-control study of individuals undergoing colonoscopy.

Age Distribution↗
PubMed2004

Beat-to-beat QT dynamics in healthy subjects.

BACKGROUND: Measures of QT dynamics express repolarization abnormalities that carry prognostic information, but the reproducibility of beat-to-beat QT dynamics has never been established. The QT interval is prolonged at night, but how the circadian rhythm and heart rate influence the dynamic QT measurements is still unsettled. The aims of the present study were: (1) to describe the reproducibility of beat-to-beat QT dynamics with respect to intrasubject, between-subject, and between-observer variability and (2) to describe the normal range, circadian variation, and heart rate dependence of QT dynamics. METHODS: Ambulatory Holter recordings were performed three times on 20 healthy volunteers and were analyzed by two experienced cardiologists. Slope and intercept of the QT/RR regression, the variability of QT and R-R intervals expressed as the standard deviation, and the relation between QT and RR variability expressed as a variability ratio were measured among other QT dynamics. RESULTS: The reproducibility of all QT dynamics was good. All QT dynamics showed circadian variation when calculated on an hourly basis. The day/night variation in slope could be explained by the differences in heart rate, whereas the day/night variation in intercept was heart rate independent. CONCLUSION: The present study shows that reliable automatic QT measurements could be performed, encouraging further evaluation of the clinical value of QT dynamics in risk stratification of cardiac patients.

Adult↗
PubMed2005

Variance components of gingival thickness.

OBJECTIVES: Distinct periodontal phenotypes have been identified by cluster analysis, which is an explorative method with very low external validity. The aim of the present study was to investigate variance components of facial gingival thickness in young adults with mild gingivitis. MATERIAL AND METHODS: Thirty-three non-smoking females, 18-23 years of age, with mild or moderate plaque-induced gingivitis participated. Gingival thickness was measured at every tooth present by use of ultrasound technology to the next 0.1 mm with a lowest measurement of 0.5 mm. Periodontal probing depth and clinical attachment level were measured with a pressure-controlled probe. Gingival bleeding index was assessed after probing on a 0-2 scale, where 1 was slight, and 2 was profuse bleeding on probing. The Silness-Loe plaque index was recorded. Multilevel variance components and random intercept models were built. RESULTS: A 2-level (subject, tooth) variance component model of gingival thickness without any explanatory variable revealed an intercept (mean) of 0.93 +/- 0.02 mm. Subject variation of gingival thickness amounted to 4.2% of the total variance. Addition of tooth- and subject-related covariates to the model revealed, after adjusting for tooth type, an association with periodontal probing depth (estimated coefficient 0.067 +/- 0.025), and considerable association with average bleeding index (-0.395 +/- 0.149) and plaque index (0.125 +/- 0.048). Variation at the tooth level was drastically reduced; subject variation amounted to 5.2%. CONCLUSION: Gingival thickness is mainly associated with tooth-related variables. Bleeding tendency is higher if gingiva is thin. Subject variability related to periodontal phenotype may add to the total variance, however, to a very low extent.

Adolescent↗