Primary Reference Standard Research Articles

Diagnostic accuracy of a prehospital electrocardiogram rule-based algorithm for ST-elevation myocardial infarction: results from a population-wide project.

This study reviewed the diagnostic accuracy of the prehospital electrocardiogram (PHECG) rule-based algorithm for ST-elevation myocardial infarction (STEMI) universally utilised in Hong Kong. This prospective observational study was linked to a population-wide project. We analysed 2210 PHECGs performed on patients who presented to the emergency medical service (EMS) with chest pain from 1 October to 31 December 2021. The diagnostic accuracy of the adopted rulebased algorithm, the Hannover Electrocardiogram System, was evaluated using the adjudicated blinded rating by two investigators as the primary reference standard. Diagnostic accuracy was also evaluated using the attending emergency physician's diagnosis and the diagnosis on hospital discharge as secondary reference standards. The prevalence of STEMI was 5.1% (95% confidence interval [CI]=4.2%-6.1%). Using the adjudicated blinded rating by investigators as the reference standard, the rule-based PHECG algorithm had a sensitivity of 94.6% (95% CI=88.2%-97.8%), specificity of 87.9% (95% CI=86.4%-89.2%), positive predictive value of 29.4% (95% CI=24.8%-34.4%), and negative predictive value of 99.7% (95% CI=99.3%-99.9%) [all P<0.05]. The rule-based PHECG algorithm that is widely used in Hong Kong demonstrated high sensitivity and fair specificity for the diagnosis of STEMI.

Measurements of Nuclear Magnetic Shielding in Molecules.

The origin of nuclear magnetic shielding in diamagnetic molecules is discussed, pointing out various contributions to the shielding from electrons and the effects of intra- and intermolecular interactions. In NMR practice, chemical shifts are determined first as the measure of shielding in observed samples. The descriptions of shielding and chemical shifts are not fully consistent. Gas phase studies permit the withdrawal of intermolecular contributions from shielding and obtaining the magnetic shielding data in isolated molecules. The shielding determination in molecules is possible using at least three methods delivering the reference shielding standards for selected nuclei. The known shielding of one magnetic nucleus can be transferred to other nuclei if the appropriate nuclear magnetic moments are available with satisfactory accuracy. It is possible to determine the nuclear magnetic dipole moments using the most advanced ab initio shielding calculations jointly with the NMR frequencies measurements for small-sized isolated molecules. Helium-3 gas is postulated as all the molecules' primary and universal reference standard of shielding. It can be easily applied using common deuterium lock solvents as the secondary reference standards. The measurements of absolute shielding are available for everyone with the use of standard NMR spectrometers.

The accuracy of prehospital triage decisions in English trauma networks – a case-cohort study

BackgroundCare for injured patients in England is provided by inclusive regional trauma networks. Ambulance services use triage tools to identify patients with major trauma who would benefit from expedited Major Trauma Centre (MTC) care. However, there has been no investigation of triage performance, despite its role in ensuring effective and efficient MTC care. This study aimed to investigate the accuracy of prehospital major trauma triage in representative English trauma networks.MethodsA diagnostic case-cohort study was performed between November 2019 and February 2020 in 4 English regional trauma networks as part of the Major Trauma Triage Study (MATTS). Consecutive patients with acute injury presenting to participating ambulance services were included, together with all reference standard positive cases, and matched to data from the English national major trauma database. The index test was prehospital provider triage decision making, with a positive result defined as patient transport with a pre-alert call to the MTC. The primary reference standard was a consensus definition of serious injury that would benefit from expedited major trauma centre care. Secondary analyses explored different reference standards and compared theoretical triage tool accuracy to real-life triage decisions.ResultsThe complete-case case-cohort sample consisted of 2,757 patients, including 959 primary reference standard positive patients. The prevalence of major trauma meeting the primary reference standard definition was 3.1% (n=54/1,722, 95% CI 2.3 – 4.0). Observed prehospital provider triage decisions demonstrated overall sensitivity of 46.7% (n=446/959, 95% CI 43.5-49.9) and specificity of 94.5% (n=1,703/1,798, 95% CI 93.4-95.6) for the primary reference standard. There was a clear trend of decreasing sensitivity and increasing specificity from younger to older age groups. Prehospital provider triage decisions commonly differed from the theoretical triage tool result, with ambulance service clinician judgement resulting in higher specificity.ConclusionsPrehospital decision making for injured patients in English trauma networks demonstrated high specificity and low sensitivity, consistent with the targets for cost-effective triage defined in previous economic evaluations. Actual triage decisions differed from theoretical triage tool results, with a decreasing sensitivity and increasing specificity from younger to older ages.

Reliability and Validity of the Hook Test for Diagnosis of Distal Biceps Tendon Ruptures

Although the initial description of the distal biceps tendon (DBT) hook test (HT) reported 100% sensitivity (Sn) and specificity (Sp), subsequent retrospective series have demonstrated imperfect validity. The purpose of this investigation was to prospectively assess the validity and reliability of the HT for complete DBT ruptures. We aimed to determine the Sn/Sp and interrater reliability for the HT. A consecutive series of adult patients presenting to our outpatient clinics with an elbow complaint was prospectively examined. Patients were included if they had undergone advanced imaging (magnetic resonance imaging or ultrasound) that imaged the DBT and underwent DBT repair. There were four participating surgeons, all of whom were blinded to magnetic resonance imaging/ultrasound prior to performing the HT. To determine the Sn/Sp of the HT and advanced imaging, intraoperative findings served as the primary reference standard. The interrater reliability of the HT was calculated for cases in which a primary examiner (surgeon) and secondary examiner (physician assistant or resident) performed the HT. Of 64 patients who had undergone advanced imaging, 28 (44%) underwent DBT surgery and were included in the assessment of Sn/Sp. The mean age was 49 years, and all patients were men. The Sn and Sp of the HT were 96% and 67%, respectively. Advanced imaging demonstrated 100% Sn and Sp. Twenty-five patients were evaluated by a primary and secondary examiner. The interrater reliability was substantial (Cohen kappa, 0.71). The Sn and Sp of the HT were 96% and 67%, respectively, when assessed prospectively. Advanced imaging findings (magnetic resonance imaging/ultrasound) demonstrated 100% Sn and Sp. The HT can be performed reliably by examiners with varying experience levels. Considering the imperfect validity of the HT, we caution against the use of this examination alone to diagnose DBT ruptures. Diagnostic II.

The Practice of Attestation Primary Reference Samples on the Example of a New Potential Analgesic Agent – 2‐({[4‐Nitrophenyl] imino}(phenyl)methyl)isoindoline‐1,3‐dione

AbstractAttestation of primary reference standard of a potential analgesic agent ‐ 2‐({[4‐nitrophenyl]imino}(phenyl)methyl)isoindoline‐1,3‐dione (TJ‐8_215) for the purpose of further use of this sample in the development and validation of analytical techniques, as well as for routine quality control of the substance TJ‐8_215 in extended preclinical studies. To calculate the attested value and its combined uncertainty by the mass balance method, the analysis of the substance TJ‐8_215 was carried out according to such indicators as authenticity (X‐ray, NMR, ESI‐MS, IR), related impurities (HPLC), residual organic solvents (GC), water, chlorides, metal impurities (AES). Kjeldahl titration and NMR spectroscopy were used as comparison methods to assess the quantitative content. The equivalence of the obtained results was proved and the attested value of the measured value calculated by the mass balance method was assigned, which was 99.6±0.3 %.

Priority accuracy by dispatch centers and Emergency Medical Services professionals in trauma patients: a cohort study

PurposePriority-setting by dispatch centers and Emergency Medical Services professionals has a major impact on pre-hospital triage and times of trauma patients. Patients requiring specialized care benefit from expedited transport to higher-level trauma centers, while transportation of these patients to lower-level trauma centers is associated with higher mortality rates. This study aims to evaluate the accuracy of priority-setting by dispatch centers and Emergency Medical Services professionals.MethodsThis observational study included trauma patients transported from the scene of injury to a trauma center. Priority-setting was evaluated in terms of the proportion of patients requiring specialized trauma care assigned with the highest priority (i.e., sensitivity), undertriage, and overtriage. Patients in need of specialized care were defined by a composite resource-based endpoint. An Injury Severity Score ≥ 16 served as a secondary reference standard.ResultsBetween January 2015 and December 2017, records of 114,459 trauma patients were collected, of which 3327 (2.9%) patients were in need of specialized care according to the primary reference standard. Dispatch centers and Emergency Medical Services professionals assigned 83.8% and 74.5% of these patients with the highest priority, respectively. Undertriage rates ranged between 22.7 and 65.5% in the different prioritization subgroups. There were differences between dispatch and transport priorities in 17.7% of the patients.ConclusionThe majority of patients that required specialized care were assigned with the highest priority by the dispatch centers and Emergency Medical Services professionals. Highly accurate priority criteria could improve the quality of pre-hospital triage.

Autonomous in situ calibration of ion‐sensitive field effect transistor pH sensors

AbstractIon‐sensitive field effect transistor‐based pH sensors have been shown to perform well in high frequency and long‐term ocean sampling regimes. The Honeywell Durafet is widely used due to its stability, fast response, and characterization over a large range of oceanic conditions. However, potentiometric pH monitoring is inherently complicated by the fact that the sensors require careful calibration. Offsets in calibration coefficients have been observed when comparing laboratory to field‐based calibrations and prior work has led to the recommendation that an in situ calibration be performed based on comparison to discrete samples. Here, we describe our work toward a self‐calibration apparatus integrated into a SeapHOx pH, dissolved oxygen, and CTD sensor package. This Self‐Calibrating SeapHOx is capable of autonomously recording calibration values from a high quality, traceable, primary reference standard: equimolar tris buffer. The Self‐Calibrating SeapHOx's functionality was demonstrated in a 6‐d test in a seawater tank at Scripps Institution of Oceanography (La Jolla, California, U.S.A.) and was successfully deployed for 2 weeks on a shallow, coral reef flat (Lizard Island, Australia). During the latter deployment, the tris‐based self‐calibration using 15 on‐board samples exhibited superior reproducibility to the standard spectrophotometric pH‐based calibration using &gt; 100 discrete samples. Standard deviations of calibration pH using tris ranged from 0.002 to 0.005 whereas they ranged from 0.006 to 0.009 for the standard spectrophotometric pH‐based method; the two independent calibration methods resulted in a mean pH difference of 0.008. We anticipate that the Self‐Calibrating SeapHOx will be capable of autonomously providing climate quality pH data, directly linked to a primary seawater pH standard, and with improvements over standard calibration techniques.

Quantitative assessment of terminal ileum motility on MR enterography in Crohn disease: a feasibility study in children.

Investigate the relationship between quantified terminal ileal (TI) motility and histopathological activity grading, Crohn Disease MRI Index (CDMI) and faecal calprotectin. Retrospective review of children with Crohn disease or unclassified inflammatory bowel disease, who underwent MR enterography. Dynamic imaging for 25 patients (median age 12, range 5 to 16) was analysed with a validated motility algorithm. The TI motility score was derived. The primary reference standard was TI Endoscopic biopsy Assessment of Inflammatory Activity (eAIS) within 40days of the MR enterography. Secondary reference standards: (1) the Crohn Disease MRI Index (CDMI) and (2) faecal calprotectin levels. MR enterography median motility score was 0.17a.u. (IQR 0.12 to 0.25; range 0.05 to 0.55), and median CDMI was 3 (IQR 0 to 5.5). Forty-three percent of patients had active disease (eAIS > 0) with a median eAIS score of 0 (IQR 0 to 2; range 0 to 5). The correlation between eAIS and motility was r = - 0.58 (p = 0.004, N = 23). Between CDMI and motility, r = - 0.42 (p = 0.037, N = 25). Motility score was lower in active disease (median 0.12 vs 0.21, p = 0.020) while CDMI was higher (median 5 vs 1, p = 0.04). In a subset of 12 patients with faecal calprotectin within 3months of MR enterography, correlation with motility was r = - 0.27 (p = 0.4). Quantified terminal ileum motility decreases with increasing histopathological abnormality in children with Crohn disease, reproducing findings in adults. TI motility showed a negative correlation with an MRI activity score but not with faecal calprotectin levels. • It is feasible to perform MRI quantified bowel motility assessment in children using free-breathing techniques. • Bowel motility in children with Crohn disease decreases as the extent of intestinal inflammation increases. • Quantified intestinal motility may be a candidate biomarker for treatment efficacy in children with Crohn disease.

Referencing of 1H and 13C NMR shielding measurements

Direct measurements of 1H, 2H and 13C NMR shielding are performed for 13 deuterated liquid solvents using an isolated helium-3 atom as the primary reference standard of shielding. It has been possible exploring the absolute resonance frequencies and nuclear magnetic moments of the investigated nuclei. The measured shielding values are verified using appropriate chemical shifts with the accurate values of 1H and 13C shielding in liquid TMS. As shown, all the new 2H shielding parameters of the investigated solvents can be applied as the secondary reference standards of shielding for gases and liquids in usual NMR laboratory practice.

Spot protein-creatinine ratio and spot albumin-creatinine ratio in the assessment of pre-eclampsia: a diagnostic accuracy study with decision-analytic model-based economic evaluation and acceptability analysis.

The National Institute for Health and Care Excellence (NICE) guidelines highlighted the need for 'large, high-quality prospective studies comparing the various methods of measuring proteinuria in women with new-onset hypertensive disorders during pregnancy'. The primary objective was to evaluate quantitative assessments of spot protein-creatinine ratio (SPCR) and spot albumin-creatinine ratio (SACR) in predicting severe pre-eclampsia (PE) compared with 24-hour urine protein measurement. The secondary objectives were to investigate interlaboratory assay variation, to evaluate SPCR and SACR thresholds in predicting adverse maternal and fetal outcomes and to assess the cost-effectiveness of these models. This was a prospective diagnostic accuracy cohort study, with decision-analytic modelling and a cost-effectiveness analysis. The setting was 36 obstetric units in England, UK. Pregnant women (aged ≥ 16 years), who were at > 20 weeks' gestation with confirmed gestational hypertension and trace or more proteinuria on an automated dipstick urinalysis. Women provided a spot urine sample for protein analysis (the recruitment sample) and were asked to collect a 24-hour urine sample, which was stored for secondary analysis. A further spot sample of urine was taken immediately before delivery. Outcome data were collected from hospital records. There were four index tests on a spot sample of urine: (1) SPCR test (conducted at the local laboratory); (2) SPCR test [conducted at the central laboratory using the benzethonium chloride (BZC) assay]; (3) SPCR test [conducted at the central laboratory using the pyrogallol red (PGR) assay]; and (4) SACR test (conducted at the central laboratory using an automated chemistry analyser). The comparator tests on 24-hour urine collection were a central test using the BZC assay and a central test using the PGR assay. The primary reference standard was the NICE definition of severe PE. Secondary reference standards were a clinician diagnosis of severe PE, which is defined as treatment with magnesium sulphate or with severe PE protocol; adverse perinatal outcome; one or more of perinatal or infant mortality, bronchopulmonary dysplasia, necrotising enterocolitis or grade III/IV intraventricular haemorrhage; and economic cost and outcomes. Health service data on service use and costs followed published economic models. In total, 959 women were available for primary analysis and 417 of them had severe PE. The diagnostic accuracy of the four assays on spot urine samples against the reference standards was similar. The three SPCR tests had sensitivities in excess of 90% at prespecified thresholds, with poor specificities and negative likelihood ratios of ≥ 0.1. The SACR test had a significantly higher sensitivity of 99% (confidence interval 98% to 100%) and lower specificity. Receiver operating characteristic (ROC) curves were similar (area under ROC curve between 0.87 and 0.89); the area under the central laboratory's SACR curve was significantly higher (p = 0.004). The central laboratory's SACR test was the most cost-effective option, generating an additional 0.03 quality-adjusted life-years at an additional cost of £45.07 compared with the local laboratory's SPCR test. The probabilistic analysis showed it to have a 100% probability of being cost-effective at the standard willingness-to-pay threshold recommended by NICE. Implementation of NICE guidelines has led to an increased intervention rate in the study population that affected recruitment rates and led to revised sample size calculations. Evidence from this clinical study does not support the recommendation of 24-hour urine sample collection in hypertensive pregnant women. The SACR test had better diagnostic performance when predicting severe pre-eclampsia. All four tests could potentially be used as rule-out tests for the NICE definition of severe PE. Testing SACR at a threshold of 8 mg/mmol should be studied as a 'rule-out' test of proteinuria. Current Controlled Trials ISRCTN82607486. This project was funded by the National Institute Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 21, No. 61. See the NIHR Journals Library website for further project information.

Evaluation of Xpert MTB/RIF assay in children with presumed pulmonary tuberculosis in Papua New Guinea

Background: The Gene Xpert MTB/ RIF assay (Xpert) is used for rapid, simultaneous detection of Mycobacterium tuberculosis (MTB) and rifampicin resistance. This study examined the accuracy of Xpert in children with suspected pulmonary tuberculosis (PTB).Methods: Children admitted to Port Moresby General Hospital with suspected PTB were prospectively enrolled between September 2014 and March 2015. They were classified into probable, possible and TB-unlikely groups. Sputum or gastric aspirates were tested by Xpert and smear microscopy; mycobacterial culture was undertaken on a subset. Children were diagnosed with TB on the basis of standard criteria which were used as the primary reference standard. Xpert, smear for acid-fast bacilli (AFB) and the Edwards TB score were compared with the primary reference standard.Results: A total of 93 children ≤14 years with suspected PTB were enrolled; 67 (72%) were classified as probable, 21 (22%) possible and 5 (5.4%) TB-unlikely. Eighty were treated for TB based on the primary reference standard. Xpert was positive in 26/93 (28%) MTB cases overall, including 22/67 (33%) with probable TB and 4/21 (19%) with possible TB. Three (13%) samples identified rifampicin resistance. Xpert confirmed more cases of TB than AFB smear (26 vs 13, p = 0.019). The sensitivity of Xpert, AFB smear and an Edwards TB score of ≥7 was 31% (25/80), 16% (13/80) and 90% (72/80), respectively, and the specificity was 92% (12/13), 100% (13/13) and 31% (4/13), respectively, when compared with the primary reference standard.Conclusion: Xpert sensitivity is sub-optimal and cannot be relied upon for diagnosing TB, although a positive result is confirmatory. A detailed history and examination, standardised clinical criteria, radiographs and available tests remain the most appropriate way of diagnosing TB in children in resource-limited countries. Xpert helps confirm PTB better than AFB smear, and identifies rifampicin resistance. Practical guidelines should be used to identify children who will benefit from an Xpert assay.

A Comparison of DSM-IV and international expert consensus diagnostic criteria for N.M.S

IntroductionNeuroleptic malignant syndrome (NMS) requires prompt recognition for effective management, but there are no established diagnostic criteria.ObjectivesTo validate the recently published international expert consensus (IEC) diagnostic criteria for NMS, which assign priority points based on the relative importance of each criterion for diagnosing NMS.AimsDetermine optimal diagnostic cutoff for priority point score.MethodsData were extracted from 221 archived telephone contact reports of clinician-initiated calls to a national telephone consultation service from 1997–2009; each case was given a total priority point score based on the IEC criteria. DSM-IV-TR research criteria, in original form and modified to accept less than ‘severe’ rigidity, served as the primary diagnostic reference standard. Consultants’ diagnoses served as an additional reference standard. The optimal priority point cutoff score was determined using receiver operating characteristic (ROC) curve analysis.ResultsArea under the ROC curve ranged from 0.715 (95% CI = 0.645–0.785, P &lt; 0.001) for consultant diagnoses to 0.857 (95% CI = 0.808–0.907, P &lt; 0.001) for modified DSM-IV-TR criteria. The latter was associated with 69.6% sensitivity and 90.7% specificity.ConclusionsAgreement was best between IEC criteria with a cutoff score of 74 and modified DSM-IV-TR criteria (sensitivity 69.6%, specificity 90.7%); this cutoff score demonstrated the highest agreement in all comparisons. Consultant diagnoses showed much better agreement with modified, compared to original, DSM-IV-TR criteria, suggesting that the DSM-IV-TR criterion of “severe” rigidity may be more restrictive than what most knowledgeable clinicians use in practice.Disclosure of interestThe authors have not supplied their declaration of competing interest.

A Validation Study of the International Consensus Diagnostic Criteria for Neuroleptic Malignant Syndrome.

Neuroleptic malignant syndrome requires prompt recognition for effective management, but there are no established diagnostic criteria. This is the first validation study of recently published international expert consensus (IEC) diagnostic criteria, which include priority points assigned on the basis of the importance of each criterion for making a diagnosis of neuroleptic malignant syndrome. Data were extracted from 221 archived telephone contact reports of clinician-initiated calls to a national telephone consultation service from 1997 to 2009; each case was given a total priority point score on the basis of the IEC criteria. Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision, (DSM-IV-TR) research criteria, in original form and modified to accept less than "severe" rigidity, served as the primary diagnostic reference standard. Consultants' diagnostic impressions were used as a secondary reference standard. Receiver operating characteristic curve analysis was used to optimize the priority point cutoff score with respect to the reference standards. Area under the receiver operating characteristic curve ranged from 0.715 (95% confidence interval, 0.645-0.785; P = 1.62 × 10) for consultant diagnoses to 0.857 (95% confidence interval, 0.808-0.907; P < 5 × 10) for modified DSM-IV-TR criteria. The latter was associated with 69.6% sensitivity and 90.7% specificity. Agreement was best between IEC criteria with a cutoff score of 74 and modified DSM-IV-TR criteria (sensitivity, 69.6%; specificity, 90.7%); this cutoff score demonstrated the highest agreement in all comparisons. Consultant diagnoses showed much better agreement with modified, compared with original, DSM-IV-TR criteria, suggesting that the DSM-IV-TR criterion of "severe" rigidity may be more restrictive than what most knowledgeable clinicians use in practice.

Whole-body diffusion-weighted MRI for staging of women with cancer during pregnancy: a pilot study

Methods Twenty patients diagnosed with cancer during pregnancy underwent WB-DWI additional to conventional imaging in this prospective single centre study. Reproducibility of WB-DWI between 2 readers was evaluated using Cohen’s statistics and accuracy was compared to conventional imaging for assessing primary tumour site, nodal metastases and visceral metastases. Histopathology after surgery or biopsy was the primary reference standard.

What is the most reliable solid culture medium for tuberculosis treatment trials?

We conducted a prospective study to determine which solid medium is the most reliable overall and after two months of therapy to detect Mycobacterium tuberculosis complex (MTB). MTB isolation and contamination rates on LJ and Middlebrook 7H10 and 7H11 agar with and without selective antibiotics were examined in a single laboratory and compared against a constructed reference standard and MGIT 960 results. Of 50 smear positive adults with pulmonary TB enrolled, 45 successfully completed standard treatment. Two spot sputum specimens were collected before treatment and at week 8 and one spot specimen each at weeks 2, 4, 6, and 12. The MTB recovery rate among all solid media for pre-treatment specimens was similar. After 8 weeks, selective (S) 7H11 had the highest positivity rate. Latent class analysis was used to construct the primary reference standard. The 98.7% sensitivity of 7H11S (95% Wilson confidence interval 96.4%-99.6%) was highest among the 5 solid media (P=0.003 by bootstrap); the 82.6% specificity of 7H10S (95% CI 75.7%-87.8%) was highest (P=0.098). Our results support 7H11S as the medium of choice. Further studies in different areas where recovery and contamination are likely to vary, are recommended.

Non-invasive investigations of potential renal artery stenosis in renal insufficiency

The diagnostic value of non-invasive methods for diagnosing renal artery stenosis in patients with renal insufficiency is incompletely known. Forty-seven consecutive patients with moderately impaired renal function and a clinical suspicion of renal artery stenosis were investigated with computed tomography angiography (CTA), gadolinium-enhanced magnetic resonance angiography (MRA), contrast-enhanced Doppler ultrasound and captopril renography. The primary reference standard was stenosis reducing the vessel diameter by at least 50% on CTA, and an alternative reference standard ('morphological and functional stenosis') was defined as at least 50% diameter reduction on CTA or MRA, combined with a positive finding from ultrasound or captopril renography. The frequency of positive findings, calculated on the basis of individual patients, was 70% for CTA, 60% for MRA, 53% for ultrasound and 30% for captopril renography. Counting kidneys rather than patients, corresponding frequencies were 53%, 41%, 29% and 15%, respectively. In relation to the CTA standard, the sensitivity (and specificity) at the patient level was 0.81 (0.79) for MRA, 0.70 (0.89) for ultrasound and 0.42 (1.00) for captopril renography, and at the kidney level 0.76 (0.82), 0.53 (0.81) and 0.30 (0.86), respectively. Relative to the alternative reference standard, corresponding values at the patient level were 1.00 (0.62) for CTA, 0.90 (0.69) for MRA, 0.91 (1.00) for ultrasound and 0.67 (1.00) for captopril renography, and at the kidney level 0.96 (0.76), 0.85 (0.79), 0.71 (0.97) and 0.50 (0.97), respectively. CTA and MRA are superior to ultrasound and captopril renography at diagnosing morphological stenosis, but ultrasound may be useful as a screening method and captopril renography for verifying renin-dependent hypertension.

AUDIT‐C as a Brief Screen for Alcohol Misuse in Primary Care

The Alcohol Use Disorders Identification Test Consumption (AUDIT-C) questions have been previously validated as a 3-item screen for alcohol misuse and implemented nationwide in Veterans Affairs (VA) outpatient clinics. However, the AUDIT-C's validity and optimal screening threshold(s) in other clinical populations are unknown. This cross-sectional validation study compared screening questionnaires with standardized interviews in 392 male and 927 female adult outpatients at an academic family practice clinic from 1993 to 1994. The AUDIT-C, full AUDIT, self-reported risky drinking, AUDIT question #3, and an augmented CAGE questionnaire were compared with an interview primary reference standard of alcohol misuse, defined as a Diagnostic and Statistical Manual, 4th ed. alcohol use disorder and/or drinking above recommended limits in the past year. Based on interviews with 92% of eligible patients, 128 (33%) men and 177 (19%) women met the criteria for alcohol misuse. Areas under the receiver operating characteristic curves (AUROCs) for the AUDIT-C were 0.94 (0.91, 0.96) and 0.90 (0.87, 0.93) in men and women, respectively (p=0.04). Based on AUROC curves, the AUDIT-C performed as well as the full AUDIT and significantly better than self-reported risky drinking, AUDIT question #3, or the augmented CAGE questionnaire (p-values <0.001). The AUDIT-C screening thresholds that simultaneously maximized sensitivity and specificity were > or =4 in men (sensitivity 0.86, specificity 0.89) and > or =3 in women (sensitivity 0.73, specificity 0.91). The AUDIT-C was an effective screening test for alcohol misuse in this primary care sample. Optimal screening thresholds for alcohol misuse among men (> or =4) and women (> or =3) were the same as in previously published VA studies.

Gonioreflectometer-based gloss standard calibration

Highly polished plane gloss standards are indispensable when using a glossmeter. The gloss value of a primary reference standard is defined by its refractive index at 589.3 nm. This definition allows ease of use, but the calibration accuracy is limited to about ±0.5% due to inconsistency between the monochromatic definition and the polychromatic use in the glossmeter. Detector-based radiometry has improved a lot in the last 20 years and it is now time to think about changing the primary gloss standard calibration to absolute specular reflectance-based measurements. This paper is a step into this direction. It shows a refractive index fitting method for gloss standards based on gonioreflectometric specular-reflection measurements, Fresnel's equation and least-squares fitting. The refractive index fitted data showed ±0.23% agreement on average with the gonioreflectometric data measured in 1° steps and ±0.07% agreement on average for the angular corrected data. The requirement for an uncertainty of ±0.1% in the gonioreflectometric calibration was also analysed.

A logistic regression model for the decision to perform access surgery

Access surgery may be recommended to about 80% of patients who present with advanced forms of periodontal disease. In this report, a multivariate logistic regression analysis which incorporated several clinical parameters for each tooth examined, i.e., tooth type, furcation involvement, bleeding on probing, attachment level, probing depth, mobility and BANA test score, was conducted using generalized estimating equations (GEE). This approach identified parameters that were significantly associated at p < 0.05 level with the need for access surgery or extraction for periodontal purposes. The estimated probabilities derived from the GEE model were plotted over the complete spectrum of operating conditions to obtain a receiver-operator characteristic (ROC) curve. At a probability cutpoint of 0.8, the decision threshold for surgery/extraction at the pretreatment examination would have a sensitivity of 76.1% and a specificity of 75.3%. We have taken this 0.8 cut point to look at specific clinical decisions made by our examiners after the patients had received scaling and root planing plus 2 weeks unsupervised usage of systemic antimicrobials. The clinicians' decision was taken as the primary reference standard. The model's estimated decision agreed with the clinicians' decision in 226 of the 284 teeth, for an accuracy of 80%. The specificity was 90% and the sensitivity was 43%.

Comparison of three DNA fluorochromes for flow cytometric estimation of nuclear DNA content in plants

Flow cytometric estimation of nuclear DNA content was performed in six plant species employing three fluorochromes showing different DNA base preferences: propidium iodide (no base preference), 4′,6‐diamidino‐2‐phenylindole (DAPI; AT preference), and mithramycin (GC preference). Nuclei isolated from human leukocytes were used as a primary reference standard. While nuclear DNA contents estimated using propidium iodide were in agreement with published data obtained using other techniques, the values obtained using fluorochromes showing base preference were significantly different. It was found that the differences were caused by the differences in overall AT/GC ratios, and by the species‐specific differences in binding of these fluorochromes to DNA. It was concluded that nuclear DNA content estimations performed with fluorochromes showing base preference should be interpreted with caution even when AT/GC ratios of the reference and the sample are equal. The use of intercalting dyes (e.g. propidium iodide) is recommended for this purpose. On the other hand, comparison of the staining behaviour of intercalating dyes with that of dyes showing base preference may give additional information on chromatin structural differences and arrangement of molecule pairs in DNA.