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In dressing plants, the rapid determination of the corrected cut point in hydrocyclone classification is desirable, useful, and important. In this work, classification tests have been carried out on white sand using a 10-cm diameter hydrocyclone to examine closely the relation between the recovery to underflow and the corrected separation size, d 50 . The study was carried out at wide ranges of: apex diameter, vortex-finder diameter, solid content of feed, and length of vortex finder. A simple, yet reliable, equation relating the solid recovery of underflow to d 50 , is developed using all the obtained results. The predicted data show good agreement with the experimental.

Density tracers are currently used in a large number of Australian coal preparation plants and research laboratories, yet few papers deal with the rigorous statistical treatment of the results from such tests. The numerical work described was carried out in order to evaluate the influence on the accuracy of derived partition data of the size of the specific gravity increment between adjacent tracers, and the number of tracers used per increment. It is shown that the sequence of tracers used in a test should be spaced at intervals not exceeding 2.5 times the expected separator E p in order to ensure that theE p is determined without bias. The influence of the number of tracers used at each specific gravity has been studied in terms of (i) the confidence intervals for individual tracer results, and (ii) the standard deviation of the cut point and E p determined when maximum likelihood estimation methods are used to fit a partition curve to the tracer results.

In this paper propositions will be established concerning the collection of all the cut points of a given planet continuum. It will be shown that there does not exist an uncountable collection of mutually exclusive subcontinua of a given continuum M each of which contains at least one cut point of M. With the aid of this fundamental theorem it is shown, among other things, that the set of all the cut points of a continuum M which are irregular points of M is necessarily countable and, indeed, that all save a countable number of the cut points of any continuum M are points of Menger order two of M.

1. By calculation and experimental verification, it has been found that there are sharp deformations of the temperature fields in the vicinities of regimes corresponding to the cut points between the limiting components, with the formation of regions with regimes of maximum purity (RMP regions). 2. In the design of towers for sharp fractionation of multicomponent mixtures, it is necessary to design for a certain reasonable excess number of trays in each section, to permit the formation of a sufficiently broad RMP region that can be placed under automatic control to ensure clean separation of the mixture into distillate and residue at the desired cut point. 3. It has been shown that, by using the properties of the RMP regions, it is possible to design an automatic control system that will give sharp fractionation at a given cut point. 4. Commercial tests of such an automatic control system have confirmed its operability and effectiveness.

The study of locally connected continua has been greatly simplified by the introduction of the cyclic element concept of G. T. Whyburn.T By definition, a cyclic element of a locally connected continuum M is any subset E of M satisfying some one of the following conditions: (1) E is a cut point of M; (2) E is an end point of M; -(3) E is any nondegenerate subcontinuum of M containing no cut point of itself which is saturated? in M with respect to this property. Every cyclic element of type (3) is called a true cyclic element. Along these lines much light has been shed upon the knotty problem of the structure of a locally connected continuum M by considering M as the sum of its cyclic elements and then deducing properties of M from the properties of cyclic elements and the known relationships which exist between them. The richness of the results in this direction has led to the hope that some still finer decomposition of locally connected continua may be possible. One such finer decomposition, based on combinatorial concepts, is given by the cyclic elements of higher order. II It is to the problem of obtaining a decomposition in the set theoretic direction that the present paper is devoted. We begin with a true cyclic element C as our space and attempt to decompose it into subsets having desirable properties. The decomposition of the space into its cyclic elements then gives the decomposition we want. This paper is but a first step towards the ultimate goal of an extensive structure theory of true cyclic elements. It explores only the most fundamen

W. M. Faucett [1] recently studied the structure of the kernel of a compact connected mob which has a point that cuts the kernel. L. W. Anderson [2] has characterized the cut point of a connected topological lattice. The main purpose of this paper is to find a lattice theoretic characterization of the kernel by means of cut points in the topological semigroups derived from topological lattices. Using the concept of B-covers [3], we shall define a suitable multiplication in topological lattices to illustrate the structure of the kernel by lattice diagrams. The fact that a special case of Faucett's Theorem (Theorem 2) can be obtained from Anderson's result (Lemma 5) is important.

It is shown that the min cone over the circle group is the only inverse semigroup or Clifford semigroup on the 2-cell with an identity whose set of idempotents has a cut point. A topological inverse semigroup S is a Hausdorff space together with a continuous associative multiplication in which each element has a unique inverse and whose idempotents commute. Such semigroups were studied in [5], which includes a characterization of inverse semigroups whose underlying space is an arc. Considering inverse semigroups on the 2-cell, the purpose of this paper is to show that the min cone over the circle group is the only inverse semigroup with an identity on the 2-cell whose set of idempotents has a cut point. Unless otherwise stated, S will denote such a semigroup and E its set of idempotents. The closure of A will be denoted by A* while other notations, definitions, and preliminary results can be found in [2], [3], and [5]. The existence of the kernel K in compact semigroups is well known, as are the facts that K is connected if S is connected, and that K consists of one s-class. It follows that K is a single point and hence S has a zero. LEMMA 1. If e is a cut point of E, then H(e) is a circle group. PROOF. Let r be the retraction of S onto E defined by r(s)=ss1l [5]. Thus r-'(e)=R(e), the a-class of e, separates S and it follows that dim R(e)=dim D(e)= 1 [3], [4]. Inversion restricted to R(e) is a homeomorphism onto L(e), so dim(L(e) x R(e))=2. The multiplication map m from L(e) x R(e) onto D(e) lowers dimension by one, so it follows that there are elements t e L(e) and s e R(e) such that m'l(ts) c H(t) x H(s) and dim m-1(ts)> 1; hence dim H(t)= dim H(s)= 1. By Green's translational lemmas, H(e) is homeomorphic to H(s), hence dim H(e)= 1 and H(e) is a circle group [1]. Let T be a min thread from 1 to 0 [6]; clearly T contains e. By Exercise 7, p. 209 of [3], SeS=eSe is a min cone over the circle group. In fact there Received by the editors February 16, 1973. AMS (MOS) subject classifications (1970). Primary 22A15; Secondary 22A99.

It is known that every bounded semi-aposyndetic plane continuum which does not separate the plane is arcwise connected. To show that this theorem remains true if the phrase “does not separate the plane” is replaced by “does not have infinitely many complementary domains” is the primary purpose of this paper.

In this note, we will define topological and virtual cut points of finite metric spaces and show that, though their definitions seem to look rather distinct, they actually coincide. More specifically, let X denote a finite set, and let D:X×X→R:(x,y)↦xy denote a metric defined on X. The tight span T(D) of D consists of all maps f∈RX for which f(x)=supy∈X(xy−f(x)) holds for all x∈X. Define a map f∈T(D) to be a topological cut point of D if T(D)−{f} is disconnected, and define it to be a virtual cut point of D if there exists a bipartition (or split) of the support supp(f) of f into two non-empty sets A and B such that ab=f(a)+f(b) holds for all points a∈A and b∈B. It will be shown that, for any given metric D, topological and virtual cut points actually coincide, i.e., a map f∈T(D) is a topological cut point of D if and only if it is a virtual cut point of D.

A continuum is 1 2 -homogeneous provided there are exactly two orbits for the action of the group of homeomorphisms of the continuum onto itself. In this paper we study some relations between 1 2 -homogeneous continua and their set of cut points. We also prove that if X is a hereditarily decomposable continuum whose proper, nondegenerate subcontinua are arc-like, then X is 1 2 -homogeneous if and only if X is an arc. Suitable examples and counterexamples are given.

We prove that every H ( i ) subset H of a connected space X such that there is no proper connected subset of X containing H , contains at least two non-cut points of X . This is used to prove that a connected space X is a COTS with endpoints if and only if X has at most two non-cut points and has an H ( i ) subset H such that there is no proper connected subset of X containing H . Also we obtain some other characterizations of COTS with endpoints and some characterizations of the closed unit interval.

The processes of hypothesis selection and testing were investigated in a simple multiple-cue learning task. Subjects learned to predict the numeric value of a criterion on the basis of a set of cues. The criterion was computed as the average of two of the cues plus random error. Following each trial, subjects were asked to select the two cues that they thought were relevant. The number of cues and the predictability of the criterion were varied factorially but, within the limits manipulated, did not affect performance to any appreciable degree. The results suggest that a subjective evaluation function based on the average of pairs of cues was operative and that a cut point was employed to decide whether to maintain or reject the current hypothesis.

Jet fuels are obtained mainly from straight-run petroleum cuts, taken in the same ratio in which they were originally present in the crude. Therefore, the initial boiling point t i and the end point t e of the cuts give an essentially unambiguous determination of the jet fuel yield. For commercial mixed West Siberian crudes, the quality indexes of which were given in [2], the dependence of fuel yield on the cut points is shown in Fig. i, with the yield of 120-240~ in the ARN-2 apparatus being taken as 100%. The yield of jet fuel (M, %) with different cut points, relative to the indicated cut, can be calculated with adequate accuracy by the formula M=0.85(ti~--I e ) (1) The arithmetic average deviation between the calculated and experimental data is no greater than 1.76%. From Eq. (i) it follows that for jet fuel of the TS-I type, an expansion of the cut point range by 10~ corresponds to an 8-9% increase in yield. In our experimental studies*, cuts with different temperature ranges (between 600C and 300~ were obtained from mixed West Siberian crudes in ARN-2 apparatus. These cuts were tested by standard methods to determine the density (02o, kg/m3), initial crystallization temperature (ticr, ~ content Of aromatic hydrocarbons (A, % by weight), lower heat of combustion (Q, kJ/kg), and closed-cup flash point (tfl , ~ From these data, graphs were plotted for the quality indexes as functions of t i and t e (Figs. ing these relationships were determined

Suppose that K is the sum of two circles in the plane tangent at the point x. (They may be "internally" or "externally" tangent.) Let D be the complementary domain of K having K as its boundary; let Q be one of the other complementary domains; and let M be the complement of D +Q. If p is a point of M not in Q and q is a point of Q, it is clear that x cuts p from q in M+Q. In fact, since M is locally connected, the existence of such a cut point follows from a wellknown separating point theorem in plane topology.2 However, if, instead of being a locally connected continuum, K is merely a continuum (possibly indecomposable), then M is not necessarily locally connected and the existence of such a cut point is not so evident or its ambiguous location gives no clue to the proof of its existence. The purpose of this paper is to state and prove a cut point existence theorem of this general nature. As is frequently the case with separating point theorems, when one weakens the hypothesis by discarding the local connectedness requirement, one must weaken the conclusion by replacing the notion of "separating point" by the notion of "cut point." But since the two notions are equivalent in the presence of local connectedness, one usually gets a stronger theorem, and this is the case here. DEFINITIONS AND NOTATION. Let space be a 2-sphere and let S denote the set of all points of the space.3 If a and b are points of a continuum M, the subset X of M-(a+b) is said to cut a from b in M provided that every subcontinuum of M containing a and b contains a point of X. When X contains only one point, it is called a cut point. If M is a continuum, by a complementary domain of M is meant a component of S-M. If D is a connected open set and Q is a connected subset of S-D, by the outer boundary of D with respect to Q is meant the boundary of the complementary domain of D containing Q.

• The measurement of high-density lipoprotein (HDL) for the purpose of assessing the risk of cardiovascular disease in the individual subject was evaluated. Three laboratory methods were compared, two electrophoretic and one heparin-manganese precipitation, and the HDL results were expressed both as a percent and as an absolute concentration. In phase 1 of the study, the optimal method and the best cut point were identified. In phase 2, these were applied to a larger population who were assigned, on the basis of clinical criteria, to a coronary heart disease and to a control group. The overall probability of correct classification of an individual by his HDL result was calculated. When HDL was expressed as a percent and determined by gel electrophoresis, 82.6% of control subjects and 83.0% of patients with coronary heart disease were classified correctly using the optimal cut point of 23.5%. ( Arch Intern Med 1982;142:469-472)

We show that only segment borders have to be taken into account as cut point candidates when searching for the optimal multisplit of a numerical value range with respect to convex attribute evaluation functions. Segment borders can be found efficiently in a linear-time preprocessing step. With training set error, which is not strictly convex, the data can be preprocessed into an even smaller number of cut point candidates, called alternations, when striving for the optimal partition. We show that no segment borders (resp. alternations) can be overlooked with strictly convex functions (resp. training set error) without risking the loss of optimality. Our experiments show that while in real-world domains a significant reduction in the number of cut point candidates can be obtained for training set error, the number of segment borders is usually not much lower than that of boundary points.

Introduction Our goal was to develop cut points for amyloid positron emission tomography (PET), tau PET, flouro-deoxyglucose (FDG) PET, and MRI cortical thickness. Methods We examined five methods for determining cut points. Results The reliable worsening method produced a cut point only for amyloid PET. The specificity, sensitivity, and accuracy of cognitively impaired versus young clinically normal (CN) methods labeled the most people abnormal and all gave similar cut points for tau PET, FDG PET, and cortical thickness. Cut points defined using the accuracy of cognitively impaired versus age-matched CN method labeled fewer people abnormal. Discussion In the future, we will use a single cut point for amyloid PET (standardized uptake value ratio, 1.42; centiloid, 19) based on the reliable worsening cut point method. We will base lenient cut points for tau PET, FDG PET, and cortical thickness on the accuracy of cognitively impaired versus young CN method and base conservative cut points on the accuracy of cognitively impaired versus age-matched CN method.

The aims were to (a) investigate associations between a novel accelerometer metric: the minimum acceleration value above which the most active 30‐minutes were accumulated during the school day (M30ACC), and health indicators, and (b) demonstrate that applying an equivalent cut‐point to the M30ACC metric gives comparable prevalence results as a moderate‐to‐vigorous physical activity (MVPA) cut‐point approach. Two hundred and ninety‐six children (age 9‐10‐years) wore wrist‐mounted accelerometers for 7‐days. School day MVPA and M30ACC were calculated. Body mass index (BMI), waist‐to‐height ratio (WHtR), and cardiorespiratory fitness (CRF) were also measured. Mixed linear models investigated associations between M30ACCand health indicators. Agreement between ranked MVPA and M30ACC values was as-sessed using percent agreement, kappa, sensitivity, and specificity statistics. M30ACCthresholds associated with health indicators were 213 mg (BMI), 206 mg (WHtR), and 269 mg (CRF) for girls. The equivalent values for boys were 234 mg (BMI), 230 mg (WHtR), and 327 mg (CRF). Less than half of girls and 75% of boys accumulated 30 minutes of school day MVPA. Just 80% of boys had M30ACC values ≥200 mg, which is equivalent to brisk walking. Agreement between MVPA and M30ACC tertiles was high, reflected by the sensitivity and specificity values of >90%. Results demonstrate the utility of M30ACC as a PA metric that is not heavily influenced by researcher decisions. M30ACC has potential as an accelerometer‐specific metric for generating PA guidelines related to health indicators and easily understood forms of activity such as brisk walking. Refereed/Peer-reviewed

Background: The London Measure of Unplanned Pregnancy (LMUP) is a psychometrically validated measure of the degree of intention of a current or recent pregnancy. The LMUP is increasingly being used worldwide, and can be used to evaluate family planning or ­preconception care programs. However, beyond recommending the use of the full LMUP scale, there is no published guidance on how to use the LMUP as an outcome measure. Ordinal logistic regression has been recommended informally, but studies published to date have all used binary logistic regression and dichotomized the scale at different cut points. There is thus a need for evidence-based guidance to provide a standardized methodology for multivariate analysis and to enable comparison of results. This paper makes recommendations for the regression method for analysis of the LMUP as an outcome measure. Materials and methods: Data collected from 4,244 pregnant women in Malawi were used to compare five regression methods: linear, logistic with two cut points, and ordinal logistic with either the full or grouped LMUP score. The recommendations were then tested on the original UK LMUP data. Results: There were small but no important differences in the findings across the regression models. Logistic regression resulted in the largest loss of information, and assumptions were violated for the linear and ordinal logistic regression. Consequently, robust standard errors were used for linear regression and a partial proportional odds ordinal logistic regression model attempted. The latter could only be fitted for grouped LMUP score. Conclusion: We recommend the linear regression model with robust standard errors to make full use of the LMUP score when analyzed as an outcome measure. Ordinal logistic regression could be considered, but a partial proportional odds model with grouped LMUP score may be required. Logistic regression is the least-favored option, due to the loss of information. For logistic regression, the cut point for un/planned pregnancy should be between nine and ten. These recommendations will standardize the analysis of LMUP data and enhance comparability of results across studies.

Background While it is recognised that depression is prevalent in Rheumatoid Arthritis (RA), recent studies have also highlighted significant levels of anxiety in RA patients. This study compared two commonly used scales, the Depression Anxiety and Stress Scale (DASS) and the Hospital Anxiety and Depression Scale (HADS), in relation to their measurement range and cut points to consider the relative prevalence of both constructs, and if prevalence rates may be due to scale-specific case definition. Methods Patients meeting the criteria for RA were recruited in Leeds, UK and Sydney, Australia and asked to complete a survey that included both scales. The data was analysed using the Rasch measurement model. Results A total of 169 RA patients were assessed, with a repeat subsample, resulting in 323 cases for analysis. Both scales met Rasch model expectations. Using the 'possible+probable' cut point from the HADS, 58.3% had neither anxiety nor depression; 13.5% had anxiety only; 6.4% depression only and 21.8% had both 'possible+probable' anxiety and depression. Cut points for depression were comparable across the two scales while a lower cut point for anxiety in the DASS was required to equate prevalence. Conclusions This study provides further support for high prevalence of depression and anxiety in RA. It also shows that while these two scales provide a good indication of possible depression and anxiety, the estimates of prevalence so derived could vary, particularly for anxiety. These findings are discussed in terms of comparisons across studies and selection of scales for clinical use.

Background: The assessment of Generalised Joint Hypermobility (GJH) is usually based on the Beighton tests, which consist of a series of nine tests. Possible methodological shortcomings can arise, as the tests do not include detailed descriptions of performance, interpretation nor classification of GJH. The purpose of this study was, among children aged 7-8 and 10-12 years, to evaluate: 1) the inter-tester reproducibility of the tests and criteria for classification of GJH for 2 variations of the Beighton test battery (Methods A and B) with a variation in starting positions and benchmarks between methods, and 2) the inter-method agreement for the two batteries. Methods: A standardised three-phase protocol for clinical reproducibility studies was followed including a training phase, an overall agreement phase and a study phase. The number of participants in the three phases was 10, 70 and 39 respectively. For the inter-method study a total of 103 children participated. Two testers judged each test battery. A score of ≥5 was set as the cut-off level for GJH. Cohen's kappa statistics and McNemar´s test were used to test for agreement and significant differences. Results: Kappa values for GJH (≥5# were 0.64 #Method A, prevalence 0.42# and 0.59 #Method B, prevalence 0.46#, with no difference between testers in Method A #p = 0.45# and B #p = 0.29#. Prevalence of GJH in the inter-method study was 31% #A# and 35% #B# with no difference between methods #p = 0.54). Conclusions: Inter-tester reproducibility of Methods A and B was moderate to substantial, when following a standardised study protocol. Both test batteries can be used in the same children population, as there was no difference in prevalence of GJH at cut point 5, when applying method A and B. However, both methods need to be tested for their predictive validity at higher cut-off levels, e.g. ≥6 and ≥7.

Background: It is difficult to compare accelerometer-derived estimates of moderate-to-vigorous physical activity (MVPA) between studies due to differences in data processing procedures. We aimed to evaluate the effects of accelerometer processing options on total and bout-accumulated time spent in MVPA in adults. Methods: 267 participants from the ProActive Trial provided 1236 days of valid physical activity (PA) data, collected using a 5-s epoch with ActiGraph GT1M accelerometers. We integrated data over 5-s to 60-s epoch lengths (EL) and applied two-level mixed effects regression models to MVPA time, defined using 1500 to 2500 counts/minute (cpm) cut-points (CP) and bout durations (BD) from 1 to 15 min. Results: Total MVPA time was lower on longer EL and higher CP (47 vs 26 min/day and 26 vs 5 min/day on 1500 vs 2500 cpm on 5-s and 60-s epoch, respectively); this could be approximated as MVPA = exp[2.197 + 0.279*log(CP) + 6.120*log(EL) - 0.869*log(CP)*log(EL)] with an 800 min/day wear-time. In contrast, EL was positively associated with time spent in bout-accumulated MVPA; the approximating equation being MVPA =exp[54.679 - 6.268*log(CP) + 6.387*log(EL) - 10.000*log(BD) - 0.162*log(EL)*log(BD) - 0.626*log(CP)*log(EL) + 1.033*log(CP)*log(BD)]. BD and CP were inversely associated with MVPA, with higher values attenuating the influence of EL. Conclusions: EL, CP and BD interact to influence estimates of accelerometer-determined MVPA. In general, higher CP and longer BD result in lower MVPA but the direction of association for EL depends on BD. Reporting scaling coefficients for these key parameters across their frequently used ranges would facilitate comparisons of population-level accelerometry estimates of MVPA.

Background:A study deriving a threshold for moderate- to vigorous-intensity physical activity (MVPA) in terms of accelerometer counts in 12-year-old children was repeated with a subset of the same children at 16 years.Methods:Fifteen girls and thirty boys took part in 6 activities (lying, sitting, slow walking, walking, hopscotch and jogging) while wearing an Actigraph 7164 accelerometer and a Cosmed K4b2 portable metabolic unit. Random intercepts modeling was used to estimate cut points for MVPA (defined as 4 METs).Results:Using a single model, the sex-specific thresholds derived for MVPA at 16 years were some way below the 3600 counts/minute used for both sexes at age 12, particularly for girls. However graphical examination suggested that a single model might be inadequate to describe both higher- and lower-intensity activities. Models using only lower-intensity activities close to the 4 METs threshold supported retention of the 3600 counts/minute cut point for both sexes.Conclusions:When restricting to lower-intensity activities only, these data do not provide sufficient evidence to change the previously established cut point of 3600 counts/minute to represent MVPA. However, further data and more sophisticated modeling techniques are required to confirm this decision.

We exhibit small size measure-once one-way quantum finite automata (mo-1qfa’s) inducing multiperiodic stochastic events. Moreover, for certain classes of multiperiodic languages, we exhibit: (i) isolated cut point mo-1qfa’s whose size logarithmically depends on the periods; (ii) Monte Carlo mo-1qfa’s whose size logarithmically depends on the periods and polynomially on the inverse of the error probability.

Two samples can be compared by selecting a cut point and forming a 2 x 2 table of the numbers of observations above and below the cut point in each sample. Different cut points correspond to the maximum chi square statistic, the maximum squared log odds ratio, and the generalized Kolmogorov-Smirnov statistic. We simulated the small-sample null distribution of these statistics. The distributions of the maximally selected chi square statistic and the squared log odds ratio statistic are compared to each other and to the large-sample results of Miller and Siegmund (1982, Biometrics 38, 1011-1016. The distributions of and agreement among the three cut points are also considered.

Two samples can be compared by selecting a cut point and then forming a 2 x 2 table of the numbers of observations above and below the cut point in each sample. When the cut point is selected so as to maximize the standard chi square statistic, the chi square percentile points are inappropriate. Actual significance levels are computed for large samples, and correct percentile pOilltS are tabulated.

In the first section of this paper, the notion of a space being rational at a point is generalized to what is here called quasi-rational at a point. It is shown that a compact metric continuum which is quasi-rational at each point of a dense subset of an open set is both connected im kleinen and semi-locally-connected on a dense subset of that open set. In the second section a G, set is constructed such that every point in the GQ at which the space is not semi-locally-connected is a cut point. A condition is given for this G, set to be dense. This condition, in addition to requiring that the space be not semi-locally-connected at any point of a dense G5 set gives a sufficient condition for the space to contain a G, set of cut points. The condition generalizes that given by Grace. 1. Throughout this paper M will be taken to be a compact metric continuum. Many of the lemmas, however, can be proven with less hypotheses. Lemma 2, for example, requires only that the sets P, (defined below) be subcontinua of M. Compact Hausdorff is sufficient for this to happen [4]. Let x, y, and z be points of M (not necessarily distinct). The point x cuts between y and z in M when every subcontinuum of M which contains both y and z must also contain x. The point x is a cut point of M when x cuts between two points distinct from x. M is said to be aposyndetic (semi-locally-connected) at x wvith respect to y if and only if there is a subcontinuum of M with x (y) in its interior that does not contain y (x). M is aposyndetic (semi-locally-connected) at x when it is aposyndetic (semi-locally-connected) at x with respect to every other point. Finally, M is connected im kleinen at x when each neighborhood of x contains a closed neighborhood of x which is also connected. One should note that when M is connected im kleinen at a point, it is also aposyndetic at that point. For x E M, P, denotes {y E M I M is not aposyndetic at y with respect to x}, and for T c M, PT denotes n {H I T c HO and H is a Received by the editors May 20, 1970. AMS 1969 subject classifications. Primary 5455.

Background While the International Diabetes Federation (IDF) has ethnic specific waist circumference (WC) cut-points for the metabolic syndrome for Asian populations it is not known whether the cut-points for black populations should differ from those for European populations. We examined the validity of IDF WC cut points for identifying insulin resistance (IR), the underlying cause of the metabolic syndrome, in predominantly black, young Jamaican adults. Methods Participants from a 1986 birth cohort were evaluated between 2005 and 2007 when they were 18-20 years old. Trained observers took anthropometric measurements and collected a fasting blood sample. IR was assessed using the homeostasis model assessment computer programme (HOMA-IR). Sex specific quartiles for IR were generated using HOMA-IR values and participants in the highest quartile were classified as "insulin resistant". Receiver operator characteristic (ROC) curves were used to estimate the best WC to identify insulin resistance. The sensitivity and specificity of these values were compared with the IDF recommended WC cut-points. Results Data from 707 participants (315 males; 392females) were analysed. In both sexes those with IR were more obese, had higher mean systolic blood pressure, glucose and triglycerides and lower mean HDL cholesterol. The WC was a good predictor of IR with an ROC area under the curve (95% CI) of 0.71(0.64,0.79) for men and 0.72(0.65,0.79) for women. Using the Youden Index (J) the best WC cut point for identifying IR in male participants was 82 cm (sensitivity 45%, specificity 93%, J 0.38) while the standard cut point of 94 cm had a sensitivity of 14% and specificity of 98% (J 0.12). In the female participants 82 cm was also a good cut point for identifying IR (sensitivity 52%, specificity 87%, J 0.39) and was similar to the standard IDF 80 cm cut point (sensitivity 53%, specificity 82%, J 0.35). Conclusions The WC that identified IR in young black men is lower than the IDF recommended WC cut point. Sex differences in WC cut points for identifying IR were less marked in this population than in other ethnic groups.