High Interobserver Concordance Research Articles

Development and Validation of a HER2-Low Focused Immunohistochemical Scoring System With High-Interobserver Concordance: The Australian HER2-Low Breast Cancer Concordance Study

The DESTINY Breast-04 trial revealed survival advantages of trastuzumab deruxtecan for women with metastatic HER2-low breast cancer (1+ or 2+ immunohistochemistry [IHC], without amplification). Although this trial applied the 2018 Americal Society of Clinial Oncology (ASCO)/College of American Pathologists (CAP) HER2 IHC scoring criteria, the subjectivity and imprecision in IHC scoring have raised concerns that patients’ treatment may be misaligned. Our group of 9 experienced breast pathologists collated a deidentified set of 60 breast cancer core biopsies from 3 laboratories, evaluated with the Ventana 4B5 HER2 assay and mostly scored locally as HER2 0 or 1+. Based on ASCO/CAP 2018 criteria and our extensive experience of reporting HER2 IHC, we specified scoring conventions for cancers with low levels of HER2 protein expression, articulating specific scoring pitfalls. Each pathologist then reviewed digitized whole slide images of the IHC slides and scored the HER2 expression for each case. At a subsequent consensus workshop, we reviewed the cases jointly to establish consensus scores for each case and determine the percentage of HER2 expressing tumor cells. Consensus was reached on all cases, with 40 classified as 1+ and 3 as 2+ (not amplified), totaling 43 (71.7%) HER2-low cancers. The remaining cases were HER2 0. In 93.3% of cases (56/60), the consensus score matched with the majority opinion of pathologists’ independent scores. Seven (41.2%) of the 17 cases reported locally as HER2 0 were classified as HER2 low. Conversely, among 32 cases with local scores of 1+, 7 (21.8%) were reclassified as ultralow or null. Individual pathologists’ accuracy in matching the consensus scores ranged from 73.3% to 91.67% (mean, 80.74%). Among HER2-low cancers those in which <20% of the tumor cells expressed HER2 had the lowest concordance levels. Observers Cohen’s κ coefficients for concordance were excellent for 4, good in 1, and moderate in the 4 observers. This reference set of cases with expert consensus HER2 scores will be invaluable for peer training and development of our national external quality assurance program for HER2-low cancers. For assessing breast cancers at the low end of HER2 protein expression, our targeted scoring criteria and explicit instruction on pitfalls improved pathologists’ accuracy and concordance.

The performance of the node reporting and data system 1.0 (Node-RADS) and DWI–MRI in staging patients with cervical carcinoma according to the new FIGO classification (2018)

PurposeTo evaluate the diagnostic accuracy of the Node-RADS score and the utility of apparent diffusion coefficient (ADC) values in predicting metastatic lymph nodes (LNs) involvement in cervical cancer (CC) patients using magnetic resonance imaging (MRI). The applicability of the Node RADS score across three readers with different years of experience in pelvic imaging was also assessed.Material and methodsAmong 140 patients, 68 underwent staging MRI, neoadjuvant chemotherapy and radical surgery, forming the study cohort. Node-RADS scores of the main pelvic stations were retrospectively determined to assess LN metastatic likelihood and compared with the histological findings. Mean ADC, relative ADC (rADC), and correct ADC (cADC) values of LNs classified as Node-RADS ≥ 3 were measured and compared with histological reports, considered as gold standard.ResultsSensitivity, specificity, positive and negative predictive values (PPVs and NPVs), and accuracy were calculated for different Node-RADS thresholds. Node RADS ≥ 3 showed a sensitivity of 92.8% and specificity of 72.5%. Node RADS ≥ 4 yielded a sensitivity of 71.4% and specificity of 100%, while Node RADS 5 yielded 42.9% and 100%, respectively. The diagnostic performance of mean ADC, cADC and rADC values from 78 LNs with Node-RADS score ≥ 3 was assessed, with ADC demonstrating the highest area under the curve (AUC 0.820), compared to cADC and rADC values.ConclusionThe Node-RADS score provides a standardized LNs assessment, enhancing diagnostic accuracy in CC patients. Its ease of use and high inter-observer concordance support its clinical utility. ADC measurement of LNs shows promise as an additional tool for optimizing patient diagnostic evaluation.

Assessment of large droplet fat in frozen sections of donor liver biopsies: utility and interobserver variability of the newly described Banff method compared to a simplified Average of Fields method

AimsThere is great variability in the assessment and reporting of fat in frozen sections of donor liver biopsies. The Banff Working Group has proposed a novel method and definition for...

High interobserver and intraobserver reproducibility among pathologists assessing PD-L1 CPS across multiple indications.

A common concern among pathologists scoring PD-L1 immunohistochemical staining is interobserver and intraobserver variability. We assessed the interobserver and intraobserver reproducibility of PD-L1 scoring among trained pathologists using a combined positive score (CPS; tumour cell and tumour-associated immune cell staining). Data were collected for 2 years (2017-2019) from 456 pathologists worldwide. Digital training encompassed unique, tumour-specific training, and test sets. Samples were stained using PD-L1 IHC 22C3 pharmDx and evaluated at specific CPS cutoffs for gastric cancer (GC), cervical cancer (CC), urothelial cancer (UC), oesophageal cancer (OC), and head and neck squamous cell carcinoma (HNSCC). Pathologists underwent expert-to-peer training and scored 20 blinded samples on day 1 and 25 blinded samples on day 2 (including 15 of the day 1 samples). Interobserver and intraobserver reproducibility were assessed. For GC (120 observers) and CC (32 observers) samples assessed at CPS ≥1, average interobserver agreement was 91.5% and 91.0%, respectively, and average intraobserver agreement was 90.2% and 96.6%, respectively. For UC (139 observers) and OC (52 observers) samples measured at CPS ≥10, average interobserver agreement was 93.4% and 93.7%, respectively, and average intraobserver agreement was 92.0% and 92.5%, respectively. For HNSCC samples (113 observers), average interobserver agreement was 94.1% at CPS ≥1 and 86.5% at CPS ≥20; intraobserver agreement was 94.7% at CPS ≥1 and 90.5% at CPS ≥20. The consistently high interobserver and intraobserver concordance rates support the effectiveness of face-to-face training of many global pathologists for scoring PD-L1 CPS across multiple indications at several specific cutoffs.

Applicability and reproducibility of the validated intraoperative bleeding severity scale (VIBe scale) in liver surgery: A multicenter study

BackgroundBleeding is an intraoperative and postoperative complication of liver surgery of concern, and yet evidence to support utility and reproducibility of bleeding scales for liver surgery is limited. We determined the reproducibility of the clinician-reported validated intraoperative bleeding severity scale and its clinical value of implementation in liver surgery. MethodsIn this descriptive and observational multicenter study, we assessed the performance of liver surgeons instructed on the clinician-reported intraoperative bleeding severity scale using training videos that covered all 5 grades of bleeding severity. Surgeons were stratified according to years of surgical experience and number of surgeries performed per year based on a median split in low and high values. Intraobserver and interobserver agreement was assessed using Kendall’s coefficient of concordance (Kendall’s W). ResultsForty-seven surgeons from 10 hospitals in Spain participated in the study. The overall intraobserver concordance was 0.985, and the overall interobserver concordance was 0.929. For “high experience” surgeons, the intraobserver and interobserver agreement values were 0.990 and 0.941, respectively. For “low experience” surgeons, the intraobserver and interobserver agreement was 0.981 and 0.922, respectively. Regarding the annual number of surgeries, intraobserver and interobserver agreement values were 0.995 and 0.940, respectively, for surgeons performing >35 surgeries per year, with 0.979 and 0.923, respectively, for surgeons who perform ≤35 surgeries year. ConclusionThe clinician-reported intraoperative bleeding severity scale shows high interobserver and intraobserver concordance, suggesting it is a useful tool for assessing severity of bleeding during liver surgery; years of surgical experience and number of annual procedures performed did not affect the applicability of the clinician-reported intraoperative bleeding severity scale.

Defining electrocardiographic criteria to differentiate non-type 1 Brugada ECG variants from normal incomplete RBBB patterns in the young SCD-SOS cohort.

We assessed the prevalence of non-type 1 Brugada pattern (T1BrP) in children and young adults from the Sudden Cardiac Death-Screening Of risk factorS cohort and the diagnostic yield of nonexpert manual and automatic algorithm electrocardiogram (ECG) measurements. Cross-sectional study. We reviewed 14 662 ECGs and identified 2226 with a rSr'-pattern in V1-V2. Among these, 115 were classified by experts in hereditary arrhythmic-syndromes as having or not non-T1BrP, and were compared with measurements of 5 ECG-derived parameters based on a triangle formed by r' -wave (d(A), d(B), d(B)/h, β-angle) and ST-ascent, assessed both automatically and manually by nonexperts. We estimated intra- and interobserver concordance for each criterion, calculated diagnostic accuracy and defined the most appropriate cut-off values. A rSr'-pattern in V1-V2 was associated with higher PQ interval and QRS duration, male gender, and lower body mass index (BMI). The manual measurements of non-T1BrP criteria were moderately reproducible with high intraobserver and moderate interobserver concordance coefficients (ICC: 0.72-0.98, and 0.63-0.76). Criteria with higher discriminatory capacity were: distance d(B) (0.72; 95% confidence interval [CI]: 0.65-0.80) and ST-ascent (0.87; 95% CI: 0.82-0.92), which was superior to the 4 r'-wave criteria together (area under curve [AUC: 0.74]). We suggest new cut-offs with improved combination of sensitivity and specificity: d(B) ≥ 1.4 mm and ST-ascent ≥ 0.7 mm (sensitivity: 1%-82%; specificity: 71%-84%), that can be automatically measured to allow classification in four morphologies with increasing non-T1BrP probability. rSr'-pattern in precordial leads V1-V2 is a frequent finding and the detection of non-T1BrP by using the aforementioned five measurements is reproducible and accurate. In this study, we describe new cut-off values that may help untrained clinicians to identify young individuals who may require further work-up for a potential Brugada Syndrome diagnosis.

Novel prognostic histopathological grading system in oral squamous cell carcinoma based on tumour budding and cell nest size shows high interobserver and intraobserver concordance

AimsSquamous cell carcinoma of the oral cavity (OSCC) is a common tumour entity with a variable, partially highly aggressive clinical course. Recently, we proposed a novel (three-tiered) clinically useful grading...

Interobserver concordance of assessments of dysplasia and blast counts for the diagnosis of patients with cytopenia: From the Japanese central review study

The diagnosis of myelodysplastic syndromes (MDS) is based on morphology and cytogenetics. However, limited information is currently available on the interobserver concordance of the assessment of dysplastic lineages (<10% or ≥10% in bone marrow (BM)). The revised International Prognostic Scoring System (IPSS-R) described a new threshold (2%) for BM blasts. However, the interobserver concordance of the categories (0–≤2% and >2–<5%) has limited data. The purpose of the present study was to investigate the assessment of dysplastic lineages and IPSS-R reproducibility. Our study was divided into two Steps. In each Step, the microscopic examinations were performed separately by two morphologists. Regarding the category of BM blasts ≤2% and >2–<5%, interobserver agreement was more than ‘moderate’ in all pairs (kappa test: 0.43–0.90). Regarding dysgranulopoiesis (dysG) and dyserythropoiesis (dysE) in BM, interobserver agreement was more than ‘moderate’ in all pairs (kappa test, dysG: 0.45–0.96, dysE: 0.45–0.81). Regarding the category of dysmegakaryopoiesis (dysMgk) in BM, interobserver agreement was more than moderate in 4 out of 5 pairs (kappa test: 0.58–1.00), and was fair for one pair (kappa test: 0.37). We consider that high interobserver concordance may be possible for the BM blast cell count (≤2% or >2–<5%) and dysplasia (<10% or ≥10%) of each lineage.

Redefining lupus nephritis: clinical implications of pathophysiologic subtypes.

Systemic lupus erythematosus (SLE) is associated with a broad spectrum of clinical and immunologic manifestations, of which lupus nephritis is the most common cause of morbidity and mortality. The development of nephritis in patients with SLE involves multiple pathogenic pathways including aberrant apoptosis, autoantibody production, immune complex deposition and complement activation. The 2003 International Society of Nephrology/Renal Pathology Society (ISN/RPS) classification system for lupus nephritis was widely accepted with high intraobserver and interobserver concordance to guide therapeutic strategy and provide prognostic information. However, this classification system is not based on the underlying disease pathophysiology. Some additional lesions that contribute to disease presentation, including glomerular crescents, podocyte injury, tubulointerstitial lesions and vascular injury, should be recognized. Although outcomes for patients with lupus nephritis have improved over the past 30 years, treatment of this disease remains challenging and is best approached on the basis of the underlying pathogenesis, which is only partially represented by the various pathological phenotypes defined by the ISN/RPS classification. Here, we discuss the heterogeneous mechanisms involved in the pathogenesis of lupus nephritis and how improved understanding of underlying disease mechanisms might help guide therapeutic strategies.

Cytomorphology review of 100 newly diagnosed lower-risk MDS patients in the European LeukemiaNet MDS (EUMDS) registry reveals a high inter-observer concordance

The European LeukemiaNet MDS (EUMDS) registry is collecting data of myelodysplastic syndrome (MDS) patients belonging to the IPSS low or intermediate-1 category, newly diagnosed by local cytologists. The diagnosis of MDS can be challenging, and some data report inter-observer variability with regard to the assessment of the MDS subtype. In order to ensure that correct diagnoses were made by the participating centres, blood and bone marrow slides of 10% of the first 1000 patients were reviewed by an 11-person panel of cytomorphologists. All slides were rated by at least 3 panel members (median 8 panel members; range 3–9). Marrow slides from 98 out of 105 patients were of good quality and therefore could be rated properly according to the WHO 2001 classification, including assessment of dysplastic lineages. The agreement between the reviewers whether the diagnosis was MDS or non-MDS was strong with an intra-class correlation coefficient (ICC) of 0.85. Six cases were detected not to fit the entry criteria of the registry, because they were diagnosed uniformly as CMML or AML by the panel members. The agreement by WHO 2001 classification was strong as well (ICC = 0.83). The concordance of the assessment of dysplastic lineages was substantial for megakaryopoiesis and myelopoiesis and moderate for erythropoiesis. Our data show that in general, the inter-observer agreement was high and a very low percentage of misdiagnosed cases had been entered into the EUMDS registry. Further studies including histomorphology are warranted.

Reporting of tumor budding in colorectal adenocarcinomas using ×40 objective: A practical approach for resource constrained set-ups.

Tumor budding (TBud) is recognized as a poor prognostic marker in colorectal cancer (CRC) with important treatment implications in Stage II cancers and malignant polyps. There are multiple propositions for bud count reporting but without an uniformly accepted system. The International TBud consensus conference (ITBCC) proposed mandatory reporting of budding on the single worst ×20 high power field (0.785 mm2 area) with a 3-tier scoring system (low/intermediate/high for 0-4, 5-9, and ≥10 buds/×20 field). Due to the lack of availability of ×20 objective, we aimed to validate a simple ×40 field count (0.236 mm2 area) for wider applicability. Bud count was done on hematoxylin and eosin-stained slides of 92 archived cases of colon cancer on the worst ×20 and ×40 fields (0.95 mm2 and 0.236 mm2 area) (hotspot method). Count for 0.785 mm2 area was calculated using ITBCC normalization factor of 1.2. Interobserver variability between two observers was assessed. Score groups for ×20 field and proposed score groups for 40× field (low/intermediate/high for 0-1, 2-4 and ≥5 buds) were compared with disease-free survival. High bud score was seen in 20.6% and 31.5% cases, respectively, using the ×20 and ×40 methods. High interobserver concordance was noted (ICC 0.95). Both the ITBCC bud score and our proposed 40× scoring correlated significantly with prognosis (P = 0.030, log-rank test). : In centers lacking 20× objective, we propose using the worst 40× hotspot method for reporting of budding for all CRCs as a simple, reproducible and prognostically significant scoring system.

Differentiation of benign and malignant skeletal lesions with quantitative diffusion weighted MRI at 3 T

ObjectivesTo investigate the accuracy of quantitative diffusion-weighted imaging with apparent diffusion coefficient (ADC) mapping for characterizing bone lesions as benign or malignant. MethodsAt 3T, 31 subjects with intramedullary lesions imaged by DWI (b-values 50, 400, 800s/mm2) were included. ADC values (minimum, mean, maximum) were recorded by three observers independently. Interobserver variability and differences between ADC values in benign and malignant lesions were assessed (unpaired t-test, receiver operating characteristic (ROC) analysis). ResultsOf 31 lesions, 18 were benign (osteoblastic (n=1), chondroid (n=6), cysts (n=4), hemangiomatosis (n=1), fibrous (n=3), eosinophilic granuloma (n=1), giant cell tumor (n=1), osteomyelitis (n=1)) and 13 were malignant (primary (n=5), metastases (n=8)). Overall, there were higher minimum (1.27×10−3mm2/s vs 0.68×10−3mm2/s, p<0.001), mean (1.68×10−3mm2/s vs 1.13×10−3mm2/s, p<0.001), and maximum (2.09×10−3mm2/s vs 1. 7×10−3mm2/s, p=0.03). ADC values in benign lesions compared with those in malignancies. ROC analysis revealed areas under the curve for minimum, mean, and maximum ADC values of 0.91, 0.85, and 0.71, respectively. ADC measurements were made with high inter-observer concordance (ρ=0.83–0.96). ConclusionQuantitative ADC maps may have predictive value for the characterization of bone lesions. Benign lesions generally have higher minimum, mean, and maximum ADC values than malignancies, with the minimum value offering the highest accuracy for characterization.

A Novel Radiographic Index for the Diagnosis of Posterior Acromioclavicular Joint Dislocations

Background: Posterior acromioclavicular (AC) joint dislocations are frequently misclassified because posterior translation of the clavicle is difficult to evaluate in Zanca radiograph views. A novel radiographic index was used in this study to accurately diagnose posterior dislocations of the AC joint. Hypothesis: This novel index has a high degree of accuracy for the diagnosis of posterior AC joint dislocations. Study Design: Cohort study (diagnosis); Level of evidence, 2. Methods: This was an analytic, descriptive study of 150 patients with different grades of AC injuries according to the Rockwood classification (30 patients for each grade of injury: I, II, III, IV, and V). The diagnosis of an AC injury was made both clinically and radiographically by using comparative Zanca and axillary views. Two measurements were performed in Zanca views: the coracoclavicular distance and the AC width distance. A width index was calculated for each patient. The Student t test, Bonferroni test, logistic regression, linear regression, and receiver operating characteristic (ROC) curves were used for statistical analysis. Forty cases were impartially selected to obtain a κ concordance value. Results: The average value of the AC width index per group (according to the Rockwood classification) was as follows: type I, 2.1% (range, –12% to 25%); type II, 4.2% (range, –19% to 29%); type III, 19.1% (range, –59% to 91%); type IV, 110.3% (range, 47% to 181%); and type V, –3.8% (range, –71% to 62%). There was a significant difference between the average width index in the patients with type IV injuries and those in the remaining groups (P < .05). The ROC curve showed that a width index of 60% has a sensitivity of 95.7% and specificity of 97.5%, with a positive predictive value of 96.7% and negative predictive value of 95.6% to predict a type IV injury. Intraobserver reliability was rated as substantial agreement for each of 3 observers; the interobserver reliability of the 3 independent raters was almost perfect. Conclusion: An AC width index of ≥60% is highly accurate for the diagnosis of a posterior AC joint dislocation, with high intraobserver and interobserver concordance.

Clinical utility of a life quality score in dogs with canine transmissible venereal tumor treated by vincristine chemotherapy

The clinical utility of a life quality score during vincristine chemotherapy of dogs with canine transmissible venereal tumor (CTVT) was investigated using 93 tumor-bearing dogs in this prospective study. At diagnosis, clinical data and the performance status were evaluated according to a modified Karnofsky score (CKS) adapted for dogs. The animals were treated with vincristine sulphate (0.025mg/kg) at weekly intervals until the tumor had macroscopically disappeared. The time until the first adverse event and death were recorded. In a pilot study, CKS revealed a high inter-observer concordance (kappa=0.735; weighted kappa=0.835). CKS permitted a detailed monitoring of adverse effects during therapy. Cox regressions showed that low performance score and reduced body weight were independent predictive factors for death during chemotherapy. The modified Karnofsky performance score is a simple and reproducible clinical instrument, able to estimate patient outcome after treatment of CTVT.

Dynamic Hydrodistention of the Ureteral Orifice: A Novel Grading System With High Interobserver Concordance and Correlation With Vesicoureteral Reflux Grade

We evaluated the usefulness and interobserver concordance of a novel grading system for dynamic ureteral hydrodistention. Between May 1, 2002 and July 1, 2008 the hydrodistention grade in 697 ureters was prospectively assigned and recorded, including H0-no hydrodistention, H1-ureteral orifice open but tunnel not evident, H2-tunnel seen only and H3-extravesical ureter visualized. Specifically 489 refluxing ureters (vesicoureteral reflux group) were compared to 100 normal control ureters (normal control group). Additionally, the posttreatment hydrodistention grade in 56 ureters in which surgery for reflux failed was compared to that in 52 ureters with successful surgery. Hydrodistention grades assigned to an additional 77 ureters by 3 blinded observers were compared to assess the interobserver concordance of this system. Vesicoureteral reflux and hydrodistention grades correlated significantly (p <0.001). Ureters with a higher reflux grade also showed a higher hydrodistention grade. The normal control group (mean +/- SEM hydrodistention grade 0.62 +/- 0.07) showed a statistically lower hydrodistention grade than the reflux groups (overall mean hydrodistention grade 2.26 +/- 0.01). Mean posttreatment hydrodistention grade in the failed reflux surgery group was statistically higher than that in the mean successful reflux surgery group (2.03 +/- 0.09 vs 1.33 +/- 0.08). By defining the degree of hydrodistention as normal (H0-H1) and abnormal (H2-H3) the concordance between observers was 95% and 96%. The dynamic hydrodistention classification is a reliable method of evaluating the presence or absence of vesicoureteral reflux as it correlates significantly with radiographic reflux grade. It has high interobserver concordance.

Evaluation of semi‐quantitative scoring system for metaiodobenzylguanidine (mIBG) scans in patients with relapsed neuroblastoma

The purpose of this study was to determine the accuracy of two semi-quantitative scoring systems to assess response to (131)I-metaiodobenzylguanidine (mIBG) therapy in recurrent neuroblastoma. Diagnostic mIBG scan pairs (n = 57) were collected for patients who underwent (131)I-mIBG therapy for relapsed neuroblastoma. Two scoring systems were designated: Method 1, which divided the body into nine segments to view osteomedullary lesions with an additional tenth segment to assess soft tissue involvement; and Method 2, which divided the body into seven segments without a corresponding compartment for soft tissue involvement. Four nuclear medicine physicians independently assigned extension and intensity scores utilizing both methods, and separately recorded their impression of whether the post-therapy scan had improved, not changed, or worsened. Inter- and intra-observer concordance and correlation with overall response and progression-free survival (PFS) were performed. Method 1 produced the highest inter-observer concordance and was used to calculate the relative extension scores (post-therapy score divided by pre-therapy score), which correlated significantly with overall response. Patients who achieved complete response (CR) or partial response (PR) (n = 21) had lower relative extension scores, compared to those without response (P < 0.001). The readers' overall impression associated highly (P < 0.001) with the relative extension scores though results were less quantitative. Concordance was higher if initial scores were >5. Relative extension score did not predict PFS. Semi-quantitative scoring of mIBG scans provides a more reliable method of assessing response in patients with relapsed neuroblastoma than qualitative impression. The reproducibility and high inter-observer concordance makes mIBG score an important component of overall response criteria in patients with recurrent neuroblastoma.

CT colonography of the normal appendix: detection and characterization

To determine the ability of CT colonography to detect and characterize the normal appendix in adults. A total of 55 patients with CT colonography examinations are analyzed. Each observer detected an appendix in 48 cases (87%), with high interobserver concordance (kappa=0.679). The appendiceal diameter varied from 3 to 12 mm (mean 6.2 mm) with wall thickness uniformly 1 mm or less. Gas filled at least part of the appendiceal lumen in 37 cases (67%), more frequently in the prone position. Appendicoliths and periappendiceal stranding were seen in 2 and 1% of cases, respectively. An appendix can be reliably identified in approximately 87% of normal adults using CO 2-insufflation CT colonography.

In Vitro Evaluation of the Accuracy of Three Electronic Apex Locators

The accuracy of three electronic apex locators (EALs) (Justy II, Root ZX, and Neosono Ultima EZ) is evaluated, together with the concordance of the measurements obtained by two different operators. Twenty single-root human teeth were used, sectioning the crown to gain access to the root canal. A first operator (A) determined the reference (or control) length (corresponding to the actual length) for each tooth, after which all teeth were measured individually and independently by the other two operators (B and C). The results obtained with each EAL and by each operator were in turn compared with the corresponding control length. The statistical analysis of the results showed EAL reliability in detecting the apex to vary from 80% to 85% and 85% to 90% (depending on the operator) for the Justy II and Neosono systems, respectively, whereas reliability was found to be 85% for the Root ZX device. These results, combined with a high interobserver concordance, suggest electronic root canal measurement to be an objective and acceptably reproducible technique.