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PubMed1998

Estimating sample size for epidemiologic studies: the impact of ignoring exposure measurement uncertainty.

Sample size requirements for epidemiologic studies are usually determined on the basis of the desired level of statistical power. Suppose, however, that one is planning a study in which the participants' true exposure levels are unobservable. Instead, the analysis will be based on an imprecise surrogate measure that differs from true exposure by some non-negligible amount of measurement error. Sample size estimates for tests of association between the surrogate exposure measure and the outcome of interest may be misleading if they are based solely on the anticipated characteristics of the distribution of surrogate measures in the study population. We examine the accuracy of sample size estimates for cohort studies in which a continuous surrogate exposure measure is subject to either classical or Berkson measurement error. In particular, we evaluate the consequences of not adjusting the sample size estimation procedure for tests based on imprecise exposure measurements to account for anticipated differences between the distributions of the true exposure and the surrogate measure in the study population. As expected, failure to adjust for classical measurement error can lead to underestimation of the required sample size. Disregard of Berkson measurement error, however, can result in sample size estimates that exceed the actual number of participants required for tests of association between the outcome and the surrogate exposure measure. We illustrate this Berkson error effect by estimating sample size for a hypothetical cohort study that examines an association between childhood exposure to radioiodine and the development of thyroid neoplasms.

Adolescent↗

PubMedDate not supplied

Immunocytochemical detection of p16INK4a protein in scraped cervical cells.

OBJECTIVE: To develop an immunocytochemical technique for p16INK4a protein detection in scraped cervical cells for cancer screening. STUDY DESIGN: We took duplicate cervical scrapes from each participant, the first for a Pap smear and the second for p16INK4a protein detection. From a 50-microL cell suspension prepared from the scrape rinsing, a 10-microL aliquot was dropped in a 5-mm-diameter circle on a glass slide, air dried and fixed in 0.1% formal saline (1 hour) and in 95% ethanol (10 minutes). Using the immunocytochemical technique, slides from 30 samples of each Pap diagnosis class were stained sequentially with mouse monoclonal anti-p16INK4a (primary antibody), biotinylated goat antimouse IgG (secondary antibody), horse-radish peroxidase-labelled streptavidin and 3,3'-diaminobenzidine and mixed hydrogen peroxide, then counterstained with hematoxylin. A positive sample had to contain > or = 3 immunoreactive cells. Results were confirmed by western blot analysis of lysates from the remaining 40 microL of each cervical cell suspension. RESULTS: Samples were grouped as control (normal cervical cells), mild dysplasia (ASCUS, LSIL) and high abnormality (HSIL, SCC). Using the immunocytochemical technique, > 95% of the positive (SiHa cells) but 0% of the negative controls (human embryonic lung fibroblast cells) showed immunoreactive cells. All slides displayed a clear background without mucus, and positive cells were stained in both the cytoplasm and nucleus. p16INK4a Protein was detected in 17 of 30 (56.67%) ASCUS and 10 of 30 (33.33%) LSIL and increased with the degree of abnormality to 93.33% (28 of 30) and 96.67% (29 of 30) in the HSIL and SCC group, respectively. Normal cervical cells and degenerated malignant cells were nonimmunoreactive. Western blot analysis confirmed similar positive samples in the low-abnormality group, while the whole high-abnormality group was immunoreactive. A sampling error might have caused the 2 HSIL and 1 SCC sample to be negative using our immunocytochemical technique. CONCLUSION: p16INK4a Protein detection in scraped cervical cells using the immunocytochemical technique correlated with western blot analysis and was nontraumatic and precise. It offers a significant diagnostic adjunct to the Pap test for cervical cancer screening.

Biomarkers, Tumor↗

PubMed1989

Sources of diagnostic error in fine needle aspiration of the thyroid.

Smears obtained from 795 patients with suspicious thyroid nodules by fine needle aspiration (FNA) of the thyroid gland were seen over a 5-year period at the UCLA Center for the Health Sciences. From 72 patients who underwent subsequent surgical excision of their nodules, inadequate or discrepant FNA diagnoses were noticed in 20 cases (27.8%). These errors could be attributed to inadequate material for diagnosis (n = 6), sampling errors (n = 2), and cytodiagnostic errors (n = 12). If the diagnosis of follicular neoplasm was treated as indeterminate for malignancy, the overall efficiency of FNA was 88.9%. All false-negative diagnoses were related to procedure (i.e., inadequate smears or missed sampling of the lesion). The frequency of inadequate smears, in turn, was strongly related to the type of physician performing the aspiration. The frequency was highest among community-based clinicians (32.4%) and lowest among hospital-based cytopathologists (6.4%). With adequate sampling, the finding of 100% sensitivity in the diagnosis of malignant neoplasms by FNA cytology reaffirms its role as the procedure of choice in the initial screening of thyroid nodules.

Adolescent↗

PubMed2003

The Effect of altering ADL thresholds on active life expectancy estimates for older persons.

OBJECTIVES: Research on disability and active life expectancy (ALE) has often criticized the measurement of disability but has rarely empirically investigated the effect of changing measurement. The purpose of this study was to determine whether altering the number of activities of daily living (ADLs) required to consider an individual "disabled" affects population-based ALE estimates after considering parametric uncertainty and sampling error. METHODS: The authors develop a Bayesian approach to estimating multistate life tables for a three-dimensional state space, using data on community-dwelling older adults from the 1989 and 1994 National Long Term Care Survey analytic files. Empirical confidence intervals for ALE are compared across 6 models using successively higher ADL cutoffs for defining individuals as being disabled. RESULTS: After considering sampling and other errors in the estimation of transition probabilities, the authors found that altering the threshold for measuring disability has relatively little effect on ALE estimates, especially with higher ADL-level thresholds and at older ages. DISCUSSION: The implications of the results include that disability measurement, including altering the definition of being disabled and possibly expanding the state space of a model, may not affect population-based estimates of ALE.

Activities of Daily Living↗

PubMed2005

Mercapturic acids of styrene in man: comparability of the results obtained by LC/MS/MS and by HPLC-fluorimeter, and stability of samples under different storage conditions.

Two analytical methods (HPLC-fluorimeter [HPLC-FLD] and tandem mass spectrometry LC/MS/MS) are available to assay phenyl-hydroxyethylmercapturic acids (PHEMAs), the mercapturic acids of styrene in humans. In the past, each method was used to check different populations of subjects, but until now no attempt has been made to compare the two methods. This study was designed to verify whether the two methods actually give comparable results. The influence of different conditions of sample storage in altering the concentration of PHEMAs was also investigated. Urine samples were collected at the beginning and at the end of the workshift from 10 workers exposed to different levels of styrene. Each sample was analysed both by LC/MS/MS after storage under different conditions (respectively, at -20 and +4 degrees C, and after repeated freezing-thawing cycles), and by HPLC-FLD (in the same conditions of storage). Strong correlations were found between the two methods both for total PHEMAs and for each of the isomers measured, including the minor (S,R)-M1. Also an alternative approach, the Bland-Altman test, confirmed the agreement between the two methods. The different storage conditions tested did not decrease the concentration of PHEMAs but, surprisingly, a clear trend to increase was shown, particularly for (R,R)-M1, (S,R)-M2 and (R,R)-M2 in samples stored at +4 degrees C for 1 week. In conclusion, the study demonstrates that the methods give comparable results. Indirectly, this confirms also the main characteristics of PHEMAs, showed in the previous experiments: low biotransformation rates of styrene into PHEMAs; large inter-individual variability; and the presence of a clear preference in the excretion of the isomers deriving from (S)-styrene oxide. PHEMAs appear stable under different storage conditions, but further studies are needed to explain the increase of levels that occurs when samples are not kept frozen. To avoid pre-analytical errors, samples collected for biomonitoring or research purposes should be frozen as soon as possible, and thawed only one time just before the analysis.

Acetylcysteine↗

PubMed1998

Fine needle aspiration cytology diagnosis of malignant lymphoma and reactive lymphoid hyperplasia.

AIMS: To assess the diagnostic accuracy of lymph node fine needle aspiration (FNA) cytology to distinguish reactive lymphoid hyperplasia from malignant lymphoma, and to evaluate the contribution of ancillary techniques applied to cytological material. METHODS: Two hundred and seventy seven consecutive lymph node FNA specimens reported to be consistent with reactive lymphoid hyperplasia (n = 213) or suggestive/diagnostic of malignant lymphoma (n = 64) were reviewed. Follow up data were obtained by case record review or by histological correlation. The value of immunocytochemistry, in situ hybridisation for immunoglobulin light chain mRNA, and polymerase chain reaction (PCR) towards the final clinicopathological diagnosis was assessed in 92, 61, and 45 cases, respectively. RESULTS: Sixty one of 67 lymphomas and 207 of 209 reactive lymph nodes were accurately diagnosed by FNA cytology. There were six false negative aspirates including three cases of follicular lymphoma, two cases of Hodgkin's disease, and one chronic lymphocytic leukaemia. Two FNA specimens considered suspicious of lymphoma proved reactive on histology or clinical follow up. One metastatic small cell carcinoma was wrongly diagnosed as lymphoma. Ancillary studies contributed to the correct diagnosis in most cases although occasional misleading results were obtained, particularly with PCR. CONCLUSIONS: FNA cytology accurately distinguished reactive lymphoid hyperplasia from malignant lymphoma in 97% of cases. However, occasional wrong diagnoses occurred owing to sampling error or misinterpretation. Ancillary studies can be applied to cytological samples and contribute to the diagnosis in most cases.

Adult↗

PubMed1991

Quantifying lung structure. Experimental design and biologic variation in various models of lung injury.

The lung is a complex organ composed of a large number of different cell types of varying size and shape. Quantification of lung structure requires an understanding of how the distribution of specific cells and their characteristics affect the accuracy of measurement made on them and how to optimize experimental design for a morphometric study. We have studied lung structural modifications in a variety of lung injuries over the last decade. Extensive quantitative data from EM morphometric studies of pulmonary tissue have been collected. These data provide a unique opportunity to study the accuracy and efficiency of methods used to quantitate lung structure. We present and discuss novel computation-intensive methods for the estimation of biologic variability, sampling error, and measurement error. A new concept, unnested analysis of variance for stratified sampling and the use of computer-based methods for statistical analysis (the bootstrap method) and optimizing experimental design (nonlinear minimization procedure) are described in this report. Examples of experimental designs with their corresponding levels of accuracy and cost are also provided. The number of samples needed for a given level of precision is affected by the volume density of the structure being measured. The most important determinant for the overall accuracy of a morphometric study is the number of animals studied. Biologic variations between samples within an animal and among animals can vary significantly as a function of the model of injury studied.

Animals↗

PubMed2004

The EDNAP mitochondrial DNA population database (EMPOP) collaborative exercises: organisation, results and perspectives.

This paper presents an overview of the organisation and the results of the collaborative exercises (CE) of the European DNA Profiling (EDNAP) Group's mitochondrial DNA population database project (EMPOP). The aim of the collaborative exercises was to determine whether uniformity of mtDNA sequencing results could be achieved among different laboratories. These were asked to sequence either the complete mtDNA control region or the two hypervariable regions HVI (16024-16365) and HVII (73-340) from DNA extracts, buccal swabs or bloodstains, proceeding in accordance with the protocol and strategies used in each individual laboratory. The results of the collaborative exercises were employed to identify possible sources of errors that could arise during the analysis and interpretation of mtDNA profiles. These findings were taken as a basis to tentatively make suitable arrangements for the construction of a high quality mtDNA database. One hundred fifty mtDNA profiles were submitted to the evaluating laboratory, and disaccording profiles were classified into four groups corresponding to the source of error: clerical errors, sample mix-ups, contaminations and discrepancies with respect to the mtDNA nomenclature. Overall, 14 disaccording haplotypes (16 individual errors) were observed. The errors included 10 clerical errors, 3 interpretation problems, 2 cases of sample mix-up and 1 case of point heteroplasmic mixture, where the 2 sequencing reactions brought inconsistent base calls. This corresponds to an error rate of 10.7% in a virtual mtDNA database consisting of the collaborative exercise results. However, this estimate is still conservative compared to conclusions drawn by authors of meanwhile numerous publications critically reviewing published mtDNA population databases. Our results and earlier published concerns strongly emphasize the need for appropriate safety regulations when mtDNA profiles are compiled for database purposes in order to accomplish the high standard required for mtDNA databases that are used in the forensic context.

Clinical Laboratory Techniques↗

PubMed2001

The development of a blend-sampling technique to assess the uniformity of a powder mixture.

This article discusses the challenges overcome during the development of a blend-sampling technique and the successful validation of the blending operation for a tablet dosage form containing 2% active ingredient. Content uniformity results are discussedfor three pilot-scale (15-kg) and seven commercial-scale (150-kg) batches of tablets. Blend and core content uniformity data from the pilot-scale batches were acceptable. For the initial commercial-scale batches, although the tablet core content uniformity data were acceptable, the blend uniformity results were poor. The blend data for these batches had very high mean values, but acceptable relative standard deviations (RSDs). This suggested that the drug was being preferentially sampled by the thief but in a consistent, reproducible manner. Extensive testing was performed on a commercial-scale development batch to identify potential causes of sampling error. The results of this testing helped define the blend-sampling technique and strategy used to validate the mixing operation.

Bias↗

PubMed2003

Detection of rare disseminated tumor cells identifies head and neck cancer patients at risk of treatment failure.

PURPOSE: This study was designed to help establish the most appropriate samples and tests to detect disseminated tumor cells (DTCs) for head and neck cancer patients. EXPERIMENTAL DESIGN: Samples of bone marrow (BM) and central venous blood (CVB), collected preoperatively, and BM and peripheral venous blood, collected 3 months transcription postoperatively, were screened for the presence of DTCs using immunocytochemistry (ICC) with a pan-cytokeratin antibody and E48 reverse transcriptase-PCR. The molecular approach was also applied to intraoperative CVB. RESULTS: The concordance between the molecular and ICC tests applied to preoperative samples, measured by Cohen's kappa, was not uniformly good, which likely reflected sampling errors, heterogeneity of E48 antigen expression, or stochastic effects. However, testing samples of BM and CVB preoperatively with the molecular or ICC approaches gave results that predicted disease-free survival and distant-metastases-free survival. Application of a single preoperative test predicted development of distant metastases, and the prediction could be improved by combining information derived from testing both CVB and BM. Applying two tests to the same sample of blood or BM served to validate the findings from a single assay but did not improve the prediction. Testing the intraoperative sample of CVB was also a sensitive predictor of distant metastases, but testing BM or blood 3 months postsurgery was not useful. CONCLUSIONS: These findings suggest that detection of DTCs pre- or intraoperatively indicates a high risk of local and distant recurrence and reduced survival in head and neck cancer.

Bone Marrow↗

PubMed1989

Fine-needle aspiration of the liver: out of the ivory tower and into the community.

This study of 160 consecutive fine-needle aspirates of localized hepatic masses analyzed the efficacy of the technique when extended into a multicenter setting. The aspirates were processed and interpreted by a single cytology service, but they were performed, under radiographic imaging, in eight different hospitals by at least 20 radiologists, few of whom had had the opportunity to acquire long-term experience. Of 108 malignancies, 101 were correctly sampled (sensitivity, 93.5%), including 30 primary hepatocellular carcinomas, 70 metastatic tumors, and 1 lymphoma. Specific benign pathologic lesions in 12 cases were amenable to cytodiagnosis. The problem of the remaining 47 samples, which contained exclusively blood, necrotic material, or normal and reactive hepatic constituents, was addressed at length. These were considered "nondiagnostic" samples in the context of aspirating focal masses. The majority had benign lesions on further study, but tumors were found in seven, all of which had been sampling errors, resulting in a negative predictive value of 82.5%. Fine-needle sampling of localized lesions, particularly neoplasms, can thus perform well in transition from single-center studies to more widespread usage in daily practice. Confident reliance on the procedure can be maintained if appropriate radiologic and cytologic facilities exist, provided that the limitations of nonneoplastic aspirates are fully understood.

Adolescent↗

PubMed2000

[Evaluation of knowledge about climacteric in Andalusian women].

OBJECTIVES: To evaluate the level of knowledge about the menopause of Andalusian women between 30 and 60 years old; and to determine their knowledge's relationship with social and demographic variables, health service use and their position as regards the climacteric. DESIGN: Cross-sectional study. PARTICIPANTS: A sample of 770 Andalusian women between 30 and 60 was chosen, for a sample error of +/- 5% and 95% confidence interval, chosen through multi-stage sampling: at random with proportionality for province and size of habitat, and sampling by age quotas and educational background. MEASUREMENTS: The principal study variable was women's level of knowledge about the menopause, evaluated through a validated test of 56 dichotomous questions. In the descriptive analysis, the mean, standard deviation and 95% CIs were obtained; in the analysis of relationships, the test of homogeneity of means, and variance and regression analysis were used. RESULTS: On a scale of 0-56, the mean on the sample was 18.17 with a standard deviation of 14.37 (95% CI: 17.15-19.17). 57.9% of the sample polled had values of low or very low level of knowledge. In the analysis of relationships, and according to the variance analysis data, we found that the level of understanding is related (p < 0.001) to age (F = 64.21), educational background (F = 131.19), type of menopause (F = 8.94), and having received information on the menopause (F = 7.57). Of these four variables it is educational background which most explains the variability in knowledge (r = 0.52, p < 0.001). However, experience of the menopause or use of the health services for the menopause do not seem to affect knowledge about the climacteric period and its treatment. CONCLUSIONS: The lack of knowledge of the menopause shown by the population studied demonstrates the need for Health Education on this stage of life. The relationships analysis leads us to conclude that the profile of women studied who knew most was someone with middle/high educational background, aged 30-40, who had had a surgical menopause, and had received information about the menopause.

Adult↗

PubMed1995

Use of spectral analysis to test hypotheses on the origin of pinnipeds.

The evolutionary origin of the pinnipeds (seals, sea lions, and walruses) is still uncertain. Most authors support a hypothesis of a monophyletic origin of the pinnipeds from a caniform carnivore. A minority view suggests a diphyletic origin with true seals being related to the mustelids (otters and ferrets). The phylogenetic relationships of the walrus to other pinniped and carnivore families are also still particularly problematic. Here we examined the relative support for mono- and diphyletic hypotheses using DNA sequence data from the mitochondrial small subunit (12S) rRNA and cytochrome b genes. We first analyzed a small group of taxa representing the three pinniped families (Phocidae, Otariidae, and Odobenidae) and caniform carnivore families thought to be related to them. We inferred phylogenetic reconstructions from DNA sequence data using standard parsimony and neighbor-joining algorithms for phylogenetic inference as well as a new method called spectral analysis (Hendy and Penny) in which phylogenetic information is displayed independently of any selected tree. We identified and compensated for potential sources of error known to lead to selection of incorrect phylogenetic trees. These include sampling error, unequal evolutionary rates on lineages, unequal nucleotide composition among lineages, unequal rates of change at different sites, and inappropriate tree selection criteria. To correct for these errors, we performed additional transformations of the observed substitution patterns in the sequence data, applied more stringent structural constraints to the analyses, and included several additional taxa to help resolve long, unbranched lineages in the tree. We find that there is strong support for a monophyletic origin of the pinnipeds from within the caniform carnivores, close to the bear/raccoon/panda radiation. Evidence for a diphyletic origin was very weak and can be partially attributed to unequal nucleotide compositions among the taxa analyzed. Subsequently, there is slightly more evidence for grouping the walrus with the eared seals versus the true seals. A more conservative interpretation, however, is that the walrus is an early, but not the first, independent divergence from the common pinniped ancestor.

Algorithms↗

PubMed1998

[Computerized tomography and magnetic resonance in the study of retroperitoneal sarcomas].

PURPOSE: We investigated the yield of CT and MRI in the diagnosis and staging of 15 patients with retroperitoneal sarcomas; these lesions are often asymptomatic and need radical surgery to avoid local recurrences. MATERIAL AND METHODS: April 1993, to September 1997, fifteen patients with retroperitoneal sarcomas were examined and then operated on. CT and CT-guided FNAB were always performed, while MRI was performed in 8 patients only. Because of the high risk of sampling errors, the bioptic specimens were immediately evaluated by a pathologist: a second sampling was required in 10 cases and a third sampling in 6 cases. MRI was performed with a .5 T system (GE Vectra); T1- and T2-weighted transverse images of the abdomen were acquired in all patients and additional coronal and sagittal images were acquired for each abnormal region. All patients underwent surgery and the pathologic diagnosis was compared with CT and MR findings. RESULTS: CT always allowed accurate location of the lesions and identification of their components, especially fat deposits. The cytologic examination of FNAB samples allowed the diagnosis of sarcoma in 12 of 15 cases. CT results were compared with MR findings in 8 patients and the latter method had better spatial definition of the abdominal masses, particularly of vascular structures, which is important for surgical planning. DISCUSSION: The present-day imaging techniques are very important to plan the surgical treatment of retroperitoneal sarcomas. In particular, CT has the advantage of high spatial resolution and excellent tissue contrast from abundant retroperitoneal fat tissue; it also permits the cytologic sampling of viable tumor tissue. However the bulk of such lesions often prevents CT from determining the tumor origin, in which case MRI provides better spatial resolution and vascular detailing, which helps surgical planning. CONCLUSIONS: Both CT and MRI are major tools in the diagnosis and staging of retroperitoneal sarcomas because they can accurately define the borders of large tumors and their relationships with surrounding organs. MRI has the advantage of characterizing the blood supply to the mass, but CT is better to guide FNAB.

Adult↗

PubMed1997

Fine-needle aspiration of thyroid nodules: correlation between cytology and histology and evaluation of discrepant cases.

BACKGROUND: The purpose of this study was to evaluate the results of thyroid fine-needle aspiration (FNA) and to determine the reasons for the discrepancies between the cytologic and histologic diagnoses. METHODS: The authors evaluated the cytologic and histologic results of 133 FNAs obtained from 92 patients who underwent subsequent thyroidectomies. RESULTS: The initial cytologic results were indeterminate in 39 of 133 cases (29%) because a neoplasm could not be ruled out. These cases corresponded histologically to 9 adenomatoid nodules (ANs), 14 follicular adenomas (FAs), and 16 malignant thyroid neoplasms. The reported FNA diagnoses of the remaining 94 cases (71%) were 48 ANs, 19 follicular neoplasms (FNs), 21 papillary carcinomas (PCs), and 6 cases of Hashimoto's thyroiditis (HT). Correlation of cytology and histology showed that 69 of 94 FNA results (73%) correlated with the histologic diagnoses, whereas 25 (27%) were discrepant. The discrepancies resulted from cytodiagnostic errors in 13 cases (52%), suboptimal smears in 11 (44%), and an FNA sampling error in 1 (4%). The false-negative rate of FNA was 19% and the false-positive rate was 6%. CONCLUSIONS: Diagnostic pitfalls and indeterminate FNA diagnoses were predominantly due to overlapping cytologic criteria between ANs, FNs, and follicular variants of PCs. Rendering a definite diagnosis on suboptimal FNA samples is also a significant source of pitfalls.

Adenoma↗

PubMed1988

Dealing with uncertainty: statistics for an aging population.

"Uncertainty in statistics and demographic projections for aging and other policy purposes comes from four sources: differences in definitions, sampling error, nonsampling error, and scientific uncertainty. Some of these uncertainties can be reduced by proper planning and coordination, but most often decisions have to be made in the face of some remaining uncertainty. Although decision makers have a tendency to ignore uncertainty, doing so does not lead to good policy-making. Techniques for estimating and reporting on uncertainty include sampling theory, assessment of experts' subjective distributions, sensitivity analysis, and multiple independent estimates." The primary geographical focus is on the United States.

Americas↗

PubMed1978

An evaluation of blood smears made by a new method using a spinner and diluted blood.

Blood smears were prepared with the use of a spinner, which rotated with a fixed velocity for a fixed time. All blood samples used for spun smears were diluted with a fixed ratio of buffered isotonic saline solution. Distribution of cells in these smears was found to be random. The average number of cells per unit area was substantially uniform from place to place on the same slide and on multiple slides made with the smae sample. The distribution of leukocytes by type was also iniform. For different blood samples, the average number of cells per unit area in the smears correlated well with the measured cell concentrations per unit volume in the samples for leukocytes, erythrocytes and platelets. Leukocyte differential counts on replicate spun smears using the same bloods also agreed to within the sampling error. They similarly agreed with differential counts on pulled smears made from undiluted samples of the same bloods. With few exceptions, erythrocytic morphology on the spun smears was comparable to that on the good areas of pulled smears made with undiluted samples of the same bloods. Nearly all the spun smears were suitable for both viual and fully automated hematologic examination for leukocytes, erythrocytes, and platelets. This was true over nearly the whole area of each spun slide. In these ways this spinner method makes smears whose consistently high quality is little affected by either the properties of the blood sample or the skill of maker.

Blood Cell Count↗

PubMedDate not supplied

Endoscopic ultrasound-guided fine needle aspiration of the pancreas. Diagnostic utility and accuracy.

OBJECTIVE: Endoscopic ultrasound-guided fine needle aspiration biopsy (EUS-FNAB) is regarded as a safe and reliable procedure for diagnosing and staging of pancreatic neoplasms. This study retrospectively evaluated both the diagnostic utility and accuracy of pancreatic EUS-FNABs and potential cytologic pitfalls when using Diff-Quik stain for on-site evaluation. STUDY DESIGN: Pancreatic EUS-FNABs performed between 1995 and 1998 were identified from the files of the Department of Pathology. All patients were studied via a linear-array ultrasound endoscope with an FNAB device. Immediate evaluation of the specimen by a pathologist using air-dried slides and Diff-Quik stain was done on all cases. An average of five passes (range, three to nine) were performed. Five cytologic categories were identified: nondiagnostic, benign, atypical, suspicious and malignant. EUS disease staging, histologic correlation and clinical follow-up were reviewed. RESULTS: Sixty-nine consecutive pancreative FNABs were evaluated in the study period. The patients comprised 38 females and 31 males with a mean age of 65 years (range, 36-83). Histologic correlation was available on 40 patients, and follow-up was available on the remaining 29. The cytologic diagnoses included: 31 malignant, 8 suspicious, 6 atypical, 20 benign and 4 nondiagnostic. Forty-three cases were true positive, 9 were true negative, 2 were false positive, and 11 were false negative. The overall sensitivity was 80% and specificity was 82%. CONCLUSION: The study showed that cytologic evaluation of pancreatic EUS-FNABs has 80% sensitivity and 82% specificity. False negative diagnosis was usually due to sampling error. A nondiagnostic cytologic diagnosis should be rendered in the absence of adequate sampling of a lesion. On-site cytologic evaluation of EUS-FNABs aids in guaranteeing specimen adequacy, and the pathologist should be trained to evaluate Diff-Quik-stained samples.

Adenocarcinoma↗