The performance of a diagnostic test in the case of a binary predictor can be evaluated using the measures of sensitivity and specificity. However, in many instances, we encounter predictors that are ...measured on a continuous or ordinal scale. In such cases, it is desirable to assess performance of a diagnostic test over the range of possible cutpoints for the predictor variable. This is achieved by a receiver operating characteristic (ROC) curve that includes all the possible decision thresholds from a diagnostic test result. In this brief report, we discuss the salient features of the ROC curve, as well as discuss and interpret the area under the ROC curve, and its utility in comparing two different tests or predictor variables of interest.
Measures of Interrater Agreement Mandrekar, Jayawant N.
Journal of thoracic oncology,
January 2011, 2011-January, 2011-Jan, 2011-01-00, Letnik:
6, Številka:
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Journal Article
Recenzirano
Odprti dostop
Kappa statistics is used for the assessment of agreement between two or more raters when the measurement scale is categorical. In this short summary, we discuss and interpret the key features of the ...kappa statistics, the impact of prevalence on the kappa statistics, and its utility in clinical research. We also introduce the weighted kappa when the outcome is ordinal and the intraclass correlation to assess agreement in an event the data are measured on a continuous scale.
OBJECTIVE To further characterize the demographics, outcomes, and prognostic factors for refractory status epilepticus (RSE). DESIGN Retrospective analysis of all the episodes of RSE treated between ...January 1, 1999, and August 30, 2011. SETTING Neurointensive care unit within a tertiary referral center, Mayo Clinic, Rochester, Minnesota. PATIENTS Refractory status epilepticus was defined as generalized convulsive or nonconvulsive status epilepticus (SE) that continued despite initial first- and second-line therapies. Exclusion criteria were aged younger than 18 years, anoxic/myoclonic SE, psychogenic SE, simple partial SE, and absence SE. MAIN OUTCOME MEASURES Functional outcome was defined by modified Rankin scale (mRS) dichotomized into good (mRS, 0-3) and poor (mRS, 4-6). Functional decline was defined as a change in mRS greater than 1 from hospital admission to discharge. RESULTS We identified 63 consecutive episodes of non–anoxic RSE in 54 patients. Anesthetic agents were used in 55 episodes (87.30%), and duration of drug-induced coma was (mean SD) 11.0 (17.9) days. In-hospital mortality was 31.75% (20 of 63 episodes). Poor functional outcome at discharge occurred in 48 of 63 episodes (76.19%). Hospital length of stay was (mean SD) 27.7 (37.3) days. Duration of drug-induced coma (P = .03), arrhythmias requiring intervention (P = .01), and pneumonia (P = .01) were associated with poor functional outcome. Prolonged mechanical ventilation was associated with mortality (P = .04). Seizure control without suppression-burst or isoelectric electroencephalogram predicted good functional recovery (P = .01). Age, history of epilepsy, previous SE, type of SE, and anesthetic drug used were not associated with functional outcome. CONCLUSIONS Three-quarters of patients with RSE have a poor outcome. Achieving control of the SE without requiring prolonged drug-induced coma or severe electroencephalographic suppression portends better prognosis.
Background. The value of rapid, panel-based molecular diagnostics for positive blood culture bottles (BCBs) has not been rigorously assessed. We performed a prospective randomized controlled trial ...evaluating outcomes associated with rapid multiplex PCR (rmPCR) detection of bacteria, fungi, and resistance genes directly from positive BCBs. Methods. A total of 617 patients with positive BCBs underwent stratified randomization into 3 arms: standard BCB processing (control, n = 207), rmPCR reported with templated comments (rmPCR, n = 198), or rmPCR reported with templated comments and real-time audit and feedback of antimicrobial orders by an antimicrobial stewardship team (rmPCR/AS, n = 212). The primary outcome was antimicrobial therapy duration. Secondary outcomes were time to antimicrobial de-escalation or escalation, length of stay (LOS), mortality, and cost. Results. Time from BCB Gram stain to microorganism identification was shorter in the intervention group (1.3 hours) vs control (22.3 hours) (P < .001). Compared to the control group, both intervention groups had decreased broad-spectrum piperacillin-tazobactam (control 56 hours, rmPCR 44 hours, rmPCR/AS 45 hours; P = .01) and increased narrow-spectrum β-lactam (control 42 hours, rmPCR 71 hours, rmPCR/AS 85 hours; P = .04) use, and less treatment of contaminants (control 25%, rmPCR 11%, rmPCR/AS 8%; P = .015). Time from Gram stain to appropriate antimicrobial de-escalation or escalation was shortest in the rmPCR/AS group (de-escalation: rmPCR/AS 21 hours, control 34 hours, rmPCR 38 hours, P < .001; escalation: rmPCR/AS 5 hours, control 24 hours, rmPCR 6 hours, P = .04). Groups did not differ in mortality, LOS, or cost. Conclusions. rmPCR reported with templated comments reduced treatment of contaminants and use of broad-spectrum antimicrobials. Addition of antimicrobial stewardship enhanced antimicrobial de-escalation. Clinical Trials Registration. NCT01898208.
Current techniques for the identification of the infecting organism in prosthetic-joint (e.g., hip or knee) infection remain insensitive. In this study of 331 surgeries involving prosthetic joint ...replacement, a new technique that sonicates the removed artificial joint is found to be more sensitive in identifying the infecting organism than are standard culture techniques.
In surgeries involving prosthetic joint replacement, a new technique that sonicates the removed artificial joint is found to be more sensitive in identifying the infecting organism than are standard culture techniques.
In the United States, 638,000 patients underwent hip or knee replacement in 2003.
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Although they may improve the quality of life, these procedures are associated with complications, including aseptic failure and prosthetic-joint infection.
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It is important to distinguish prosthetic-joint infection from other causes of joint failure, because its management is different.
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Nonmicrobiologic methods developed for diagnosing native-joint infection use different criteria from those used to diagnose prosthetic-joint infection.
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Microbiologic diagnosis of prosthetic-joint infection may also require different criteria from those used for the microbiologic diagnosis of native-joint infection.
Most clinicians and laboratory workers culture periprosthetic tissue (hereafter referred to as . . .
Metagenomic shotgun sequencing has the potential to transform how serious infections are diagnosed by offering universal, culture-free pathogen detection. This may be especially advantageous for ...microbial diagnosis of prosthetic joint infection (PJI) by synovial fluid analysis since synovial fluid cultures are not universally positive and since synovial fluid is easily obtained preoperatively. We applied a metagenomics-based approach to synovial fluid in an attempt to detect microorganisms in 168 failed total knee arthroplasties. Genus- and species-level analyses of metagenomic sequencing yielded the known pathogen in 74 (90%) and 68 (83%) of the 82 culture-positive PJIs analyzed, respectively, with testing of two (2%) and three (4%) samples, respectively, yielding additional pathogens not detected by culture. For the 25 culture-negative PJIs tested, genus- and species-level analyses yielded 19 (76%) and 21 (84%) samples with insignificant findings, respectively, and 6 (24%) and 4 (16%) with potential pathogens detected, respectively. Genus- and species-level analyses of the 60 culture-negative aseptic failure cases yielded 53 (88%) and 56 (93%) cases with insignificant findings and 7 (12%) and 4 (7%) with potential clinically significant organisms detected, respectively. There was one case of aseptic failure with synovial fluid culture growth; metagenomic analysis showed insignificant findings, suggesting possible synovial fluid culture contamination. Metagenomic shotgun sequencing can detect pathogens involved in PJI when applied to synovial fluid and may be particularly useful for culture-negative cases.
infection is mainly diagnosed noninvasively, with susceptibility testing traditionally requiring endoscopy. Treatment is empirical, with clarithromycin-based triple therapy recommended where ...resistance rates are below 15%. Rising rates of clarithromycin resistance, resulting in high clarithromycin-based therapy failure rates, are seen worldwide, but U.S. data are limited. We developed a real-time PCR assay for simultaneous detection of
and genotypic markers of clarithromycin resistance directly from stool specimens. The assay was validated by testing 524 stool samples using an
stool antigen test as the reference method for detection accuracy and Sanger sequencing to confirm genotypic susceptibility results. A separate set of 223 antigen-positive stool samples was tested and retrospective medical record review conducted to define clinical utility. PCR resulted in 88.6% and 92.8% sensitivity in the validation and clinical study sets, respectively. Sequencing confirmed correct detection of clarithromycin resistance-associated mutations in all positive validation samples. The PCR-predicted clarithromycin resistance rate was 39% in the clinical data set overall and 31% in treatment-naive patients; the clarithromycin-based triple therapy eradication rate in treatment-naive patients was 62%. The clarithromycin-based triple therapy success was lower when resistance was predicted by PCR (41%) than when no resistance was predicted (70%;
= 0.03). PCR results were positive in 98% of antigen-positive stools from patients tested for eradication. The described PCR assay can accurately and noninvasively diagnose
, provide genotypic susceptibility, and test for eradication. Our findings support the need for susceptibility-guided therapy in our region if a clarithromycin-based regimen is considered.
Background & Aims Crohn's disease often involves the terminal ileum (TI), but skipping of the distal TI can occur. This can lead to negative results from ileocolonoscopy. We analyzed advanced ...cross-sectional images to determine how frequently this occurs. Methods We analyzed data from 189 consecutive patients (55% women) with Crohn's disease, evaluated in 2009 by computed tomography enterography (CTE) and ileocolonoscopy. The discharge impression of the gastroenterologist who treated the patients was used as the reference standard for Crohn's disease activity. Results Of the patients evaluated, 153 underwent TI intubation during endoscopy; 67 of these (43.8%) had normal results from ileoscopy, based on endoscopic appearance. Despite their normal results from ileoscopy, 36 of these patients (53.7%) had active, small-bowel Crohn's disease. The ileum appeared normal at ileoscopy because the disease had skipped the distal ileum of 11 patients (30.6%), developed only in the intramural and mesenteric distal ileum of 23 patients (63.9%), and appeared only in the upper gastrointestinal region of 2 patients (5.6%). These patients had a shorter duration of disease (61.1% for less than 5 years) compared with those found to have Crohn's disease based on ileoscopy (41.1% for less than 5 years; P < .05). CTE detected extracolonic Crohn's disease in 26% of patients; 14% of patients were found to have disorders unrelated to inflammatory bowel disease that warranted further investigation or consultation (including 4 cancers). Conclusions Ileoscopy examination can miss Crohn's disease of the TI because the disease can skip the distal ileum or is confined to the intramural portion of the bowel wall and the mesentery. CTE complements ileocolonoscopy in assessing disease activity in patients with Crohn's disease.
Despite known low sensitivity, culture of periprosthetic tissue specimens on agars and in broths is routine. Culture of periprosthetic tissue samples in blood culture bottles (BCBs) is potentially ...more convenient, but it has been evaluated in a limited way and has not been widely adopted. The aim of this study was to compare the sensitivity and specificity of inoculation of periprosthetic tissue specimens into blood culture bottles with standard agar and thioglycolate broth culture, applying Bayesian latent class modeling (LCM) in addition to applying the Infectious Diseases Society of America (IDSA) criteria for prosthetic joint infection. This prospective cohort study was conducted over a 9-month period (August 2013 to April 2014) at the Mayo Clinic, Rochester, MN, and included all consecutive patients undergoing revision arthroplasty. Overall, 369 subjects were studied; 117 (32%) met IDSA criteria for prosthetic joint infection, and 82% had late chronic infection. Applying LCM, inoculation of tissues into BCBs was associated with a 47% improvement in sensitivity compared to the sensitivity of conventional agar and broth cultures (92.1 versus 62.6%, respectively); this magnitude of change was similar when IDSA criteria were applied (60.7 versus 44.4%, respectively; P = 0.003). The time to microorganism detection was shorter with BCBs than with standard media (P < 0.0001), with aerobic and anaerobic BCBs yielding positive results within a median of 21 and 23 h, respectively. Results of our study demonstrate that the semiautomated method of periprosthetic tissue culture in blood culture bottles is more sensitive than and as specific as agar and thioglycolate broth cultures and yields results faster.
Prosthetic joint infections are a devastating complication of arthroplasty surgery. Despite this, current microbiological techniques to detect and diagnose infections are imperfect. This study examined a new approach to diagnosing infections, through the inoculation of tissue samples from around the prosthetic joint into blood culture bottles. This study demonstrated that, compared to current laboratory practices, this new technique increased the detection of infection. These findings are important for patient care to allow timely and accurate diagnosis of infection.
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