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PubMed1998

The potential diagnostic use of K-ras codon 12 and p53 alterations in brush cytology from the pancreatic head region.

It can be difficult to distinguish between malignant and benign disease of the region of the head of the pancreas using conventional methods. K-ras and p53 alterations occur frequently in malignancies in this region and are therefore candidate tumour markers. To define the utility of these alterations in interpreting pancreatic head cytology, the present study investigated to what extent alterations in the carcinomas were detectable on cytology and whether the alterations found in the cytology came from the carcinomas. Fifty-seven consecutive pancreaticoduodenectomy resection specimens (52 with a malignancy and five without) and the ductal brush cytology specimens collected post-operatively from these resection specimens were compared for the presence of K-ras and p53 alterations. K-ras mutations were detected using the polymerase chain reaction (PCR) and allele-specific oligonucleotide hybridization, and p53 alterations using immunochemical staining for the p53 gene product. After discrepancy analysis, the results from the resection specimens and corresponding brush cytology specimens were identical in 88 per cent for the K-ras analysis and in 84 per cent for the p53 analysis. In two cases, K-ras mutations found in the brush cytology specimens were not derived from the carcinoma but from pancreatic ductal hyperplasias. Intratumour heterogeneity and sampling error were also identified as causes for discrepant results. The five resection specimens without a malignancy and the corresponding brush cytology specimens were negative for both genetic alterations. In conclusion, the detection of K-ras and p53 alterations in cells obtained from the pancreatic head region might be a valuable adjunct to conventional cytology for the diagnosis of malignancies in the pancreatic head region. However, intratumour heterogeneity, mucinous pancreatic duct hyperplasia harbouring K-ras mutations, and sampling error will hinder their diagnostic accuracy in routine clinical use.

Aged↗
PubMed1997

The results of intraoperative consultations in 181 ductal carcinomas in situ of the breast.

BACKGROUND: The utility of frozen section (FS) examination in the intraoperative management of breast lesions is well established. The accuracy of FS in the diagnosis of borderline noninvasive or preinvasive breast lesions is uncertain. METHODS: The authors retrospectively reviewed the results of intraoperative consultations/frozen section examinations of 181 ductal carcinomas in situ (DCIS) of the breast. Various clinical and pathologic factors were analyzed and correlated with FS diagnosis. RESULTS: FS examination was performed on 153 cases (85%) and only macroscopic examination on 28 cases (15%). FS diagnoses were as follows: DCIS in 76 cases (50%), atypical ductal hyperplasia/suspicious for DCIS in 8 cases (5%), benign in 55 cases (36%), deferred in 13 cases (8%), and invasive carcinoma in 1 case. FS accuracy, false-negative rate, and false-positive rate were 55%, 36%, and 0.6%, respectively. Sampling error was the main reason for the low detection rate, and technical inadequacy was a major factor contributing to interpretive problems. In multivariate regression analysis, FS accuracy was significantly associated with the clinical presentation of a palpable mass (odds ratio [OR] = 4.16, 95% confidence interval [CI]: 2.04-8.45), the macroscopic finding of a mass (OR = 3.03, 95% CI: 1.45-6.67), and necrosis (OR = 3.13, 95% CI: 1.4-6.67). CONCLUSIONS: The authors concluded that the accuracy of FS diagnosis of DCIS was low, mainly due to sampling error. In general, FS examination should not be performed when no lesion/mass is identified by macroscopic examination.

Adolescent↗
PubMed1993

Magnetic resonance spectroscopy detects cancer in draining lymph nodes.

The spread of cancer cells to draining lymph nodes is an important prognostic factor for many cancers and influences postoperative therapy in patients. Histopathology is used routinely to assess if lymph nodes contain metastases. There are, however, time and resource constraints on the volume of lymph node tissue that can be examined by the pathologist in a routine laboratory (less than 2% of each node), thus major sampling errors are possible. Conventional histopathology also relies on identifying aggregates of malignant cells for a positive diagnosis. Proton (1H) magnetic resonance (MR) spectroscopy can detect chemical changes, specifically increased levels of lactate, choline, fucose and amino acids, in lymph nodes infiltrated by cancer. Increase in lactate indicates the presence of anaerobically respiring cells, whereas choline reports that the cells are replicating. Since MR spectroscopy can identify early infiltration by malignant cells, before cell clusters are visible under the light microscope, it detects micrometastases in lymph nodes missed histopathologically. Furthermore, MR spectroscopy eliminates sampling errors since the entire lymph node is examined.

Adenocarcinoma↗
PubMed1989

An explanation for the problem of false-negative cervical smears.

False-negative cervical cytology due to sampling error is a well-recognized problem. Forty-seven women with histologically proven cervical intraepithelial neoplasia (CIN) were studied. All had two cervical smears performed at a mean interval of 3 months. At the time of the second smear, cervicography, colposcopy and biopsy were performed. The area of acetowhite cervical lesions and of the total visible atypical transformation zone (ATZ) were measured from the cervical photographs. The 17 women in whom one or both smears showed no dyskaryosis were found to have a significantly smaller proportion of their ATZ affected by CIN. It is suggested that this finding can account for the sampling error which causes false-negative cervical cytology. New screening techniques, such as cervicography, may offer a method of detecting and assessing these relatively smaller cervical lesions.

Biopsy↗
PubMed2005

Contiguous lesions in lentigo maligna.

BACKGROUND: Determining the best biopsy technique for a suspected lentigo maligna can be challenging. Because complete excisional biopsy is rarely practical, the physician is left to choose an appropriate area to biopsy. Sampling error can have devastating consequences, especially if the biopsy demonstrates a pigmented lesion that was considered in the clinical differential diagnosis. The presence of a solar lentigo, pigmented actinic keratosis, or reticulated seborrheic keratosis could mislead the pathologist and clinician to the erroneous conclusion that the incisional specimen is representative of the whole, and that no lentigo maligna is present. OBJECTIVE: We have often observed the presence of a contiguous pigmented lesion adjacent to lentigo maligna. The current study was designed to determine how frequently this phenomenon occurs. METHODS: We studied Mohs debulking specimens of lentigo maligna, and broad shave biopsy specimens of pigmented lesions on heavily sun-damaged areas of the skin proven to be lentigo maligna. RESULTS: Contiguous pigmented lesions were present in 48% of the specimens. The most common lesion was a benign solar lentigo (30%), followed by pigmented actinic keratosis (24%). CONCLUSION: Recognition of this phenomenon may prevent misdiagnosis of lentigo maligna related to sampling error.

Biopsy↗
PubMed1983

Classical statistical considerations in medical decision models.

The influence of sampling error on decision-analytic models was investigated to determine how these errors affect model reliability. Formulas were developed to relate statistical error in the probability decision threshold and gain in expected utility to the error in the data samples upon which such models are based. The formulas were validated in a simulation experiment and then applied to a hypothetical decision model and to the clinical problem of immediate surgery versus continued observation in suspected acute appendicitis. The results of this analysis show that modest statistical error affecting any variable in a decision model may be amplified into a substantially larger error in both the probability decision threshold and the gain in utility predicted by the model. In addition, when errors are present simultaneously in several variables, they may compound to unexpectedly large magnitudes, rendering the model unreliable over a wide range of disease probability. The interpretation of the results of a decision analysis should be viewed along a continuum that takes into account both the magnitude of the gain or loss in expected utility predicted by the model and a quantitative measure of the reliability of this prediction. Whenever possible, a determination of statistical error should be an integral part of any formal decision analysis.

Acute Disease↗
PubMed1997

Stereotactic core biopsy of the breast: results of one-year follow-up of 101 patients.

Stereotactic core biopsy (SCB) is being used as a cost-effective alternative to needle localized biopsy (NLB). However, an area of concern is the potential for sampling error, with sparse surgical data available concerning follow-up and failure rates. We therefore reviewed our results in patients undergoing SCB for mammographically detected breast abnormalities. Between January 1994 and February 1995, 128 patients underwent SCB. Average age was 56.4 years. Nine patients (7.0%) had histologic evidence of malignancy, with 111 (86.7%) benign diagnoses requiring no further initial intervention. Eight patients (6.3%) proceeded directly to NLB, five because of technical failure of SCB and three because of suspicious initial histology. One of the latter patients had ductal carcinoma in situ. The remaining 111 SCB patients were evaluated at 6 months and 1 year by mammographic and physical examination. Ten patients were lost to follow-up. Of the remaining 101 patients, 98 (97%) had stable mammograms and normal physical examinations. Three patients (3.9%) required subsequent NLB due to progression of the mammographic lesion. Two cases were histologically benign, and 1 patient had ductal carcinoma in situ adjacent to the previous SCB biopsy site. An additional patient underwent NLB for a new radiographic abnormality at a separate location in the ipsilateral breast, which was invasive ductal carcinoma. SCB appears to be an effective alternative to NLB for the majority of patients deemed eligible. Careful mammographic follow-up is warranted for these patients given the small, but real, possibility of sampling error.

Adult↗
PubMed2004

Stereotactic biopsy guidance in adults with supratentorial nonenhancing gliomas: role of perfusion-weighted magnetic resonance imaging.

OBJECT: The. diagnosis of low-grade glioma (LGG) cannot be based exclusively on conventional magnetic resonance (MR) imaging studies, and target selection for stereotactic biopsy is a crucial issue given the high risk of sampling errors. The authors hypothesized that perfusion-weighted imaging could provide information on the microcirculation in presumed supratentorial LGGs. METHODS: All adult patients with suspected (nonenhancing) supratentorial LGGs on conventional MR imaging between February 2001 and February 2004 were included in this study. Preoperative MR imaging was performed using a dynamic first-pass gadopentate dimeglumine-enhanced spin echo-echo planar perfusion-weighted sequence, and the tumors' relative cerebral blood volume (rCBV) measurements were expressed in relation to the values observed in contralateral white matter. In patients with heterogeneous tumors a stereotactic biopsy was performed in the higher perfusion areas before resection. Among 21 patients (16 men and five women with a mean age of 36 years, range 23-60 years), 10 had diffuse astrocytomas (World Health Organization Grade II) and 11 had other LGGs and anaplastic gliomas. On perfusion-weighted images demonstrating heterogeneous tumors, areas of higher rCBV focus were found to be oligodendrogliomas or anaplastic astrocytomas on stereotactic biopsy; during tumor resection, however, specimens were characterized predominantly as astrocytomas. Diffuse astrocytomas were associated with significantly lower mean rCBV values compared with those in the other two lesion groups (p < 0.01). The rCBV ratio cutoff value that permitted better discrimination between diffuse astrocytomas and the other lesion groups was 1.2 (80% sensitivity and 100% specificity). CONCLUSIONS: Perfusion-weighted imaging is a feasible method of reducing the sampling error in the histopathological diagnosis of a presumed LGG, particularly by improving the selection of targets for stereotactic biopsy.

Adult↗
PubMed2003

The relationship of prostate gland volume to extended needle biopsy on prostate cancer detection.

PURPOSE: We investigated the relationship between prostate volume and cancer detection by needle biopsy, and determined the effect of an increased number of cores on the sampling error of needle biopsy on large prostate glands. MATERIALS AND METHODS: The study cohort included 750 consecutive patients who underwent first time transrectal ultrasound guided prostate needle biopsy from January 1995 to August 2001. Prostate volumes were divided into quartiles (13 to 34, 34.1 to 45, 45.1 to 64 and 64.1 to 244 cc). Multivariate analysis controlling for age, prostate specific antigen (PSA) and biopsy indication was performed to determine the effect of the number of cores and prostate volume on prostate cancer detection. RESULTS: Patients diagnosed with prostate cancer were older (p = 0.0035) and had higher PSA levels (p = 0.0002) than those with no cancer on biopsy. Decreasing cancer detection rates were seen with increasing prostate volume (p = 0.0074). The OR of detection for each additional core was 0.99 (95% CI 0.93, 1.06), suggesting that increasing the number of biopsy cores did not increase the rate of prostate cancer detection. Multivariate analysis revealed that patients with larger prostates had the same, or possibly lower, cancer detection rate as the number of biopsy cores was increased. Patients with larger prostates were older (p <0.0001), had higher PSA levels (p <0.0001) and were even more likely to have undergone biopsy for increased PSA rather than abnormal digital rectal examination alone (p <0.0001). CONCLUSIONS: Our study suggests that the lower cancer detection rate for men with large prostates may be due to a decrease in the use of increased serum PSA for prostate cancer detection in larger prostates in addition to other factors such as sampling error. Increased serum PSA levels in cases of larger prostates, although a risk factor for prostate cancer warranting biopsy, may also be due to nonmalignant sources such as benign prostatic hyperplasia.

Age Factors↗
PubMed2006

Enhanced magnification-directed biopsies do not increase the detection of intestinal metaplasia in patients with GERD.

BACKGROUND: The diagnosis of Barrett's esophagus (BE) requires histologic confirmation of specialized intestinal metaplasia (SIM) through biopsy, a technique prone to sampling error. One method designed to improve the yield of biopsy uses acetic acid with magnification endoscopy: enhanced magnification endoscopy (EME). This technique identifies several mucosal surface patterns, and of these, pattern types III and IV have been associated with SIM. METHODS: We conducted a prospective, randomized trial to compare EME-directed biopsies and standard endoscopy with random biopsies in patients with symptoms of gastroesophageal reflux disease. Patients in the standard endoscopy group with evidence of BE had four-quadrant random biopsies taken every 2 cm. If there was no BE, four-quadrant biopsies were taken at the SCJ. Patients in the EME group had the mucosa at the SCJ classified as type I-IV based on published criteria. Biopsies targeted to type III and IV were compared to random biopsies. RESULTS: One hundred thirty-seven patients enrolled (68 randomized to EME, 69 to standard endoscopy). Fifty-six (41%) had endoscopic evidence of BE (20 standard endoscopy [29%] vs 36 EME [53%]). Of the patients with apparent BE, standard endoscopy with random biopsies confirmed SIM in 12 (60%) compared to 11 of 18 (61%) patients with EME targeted biopsies of patterns type III or IV (p = 1.0). Patients without apparent BE (N = 81) had SIM of the SCJ confirmed in 16% (8 of 49) with standard endoscopy and random biopsies compared with 8% (1 of 12) using EME-directed biopsy of pattern III or IV (p = 0.67). CONCLUSIONS: Random biopsies of endoscopically apparent BE and a normal SCJ yield SIM at the same rate as targeted biopsies with EME in patients with pattern types III or IV. This calls into question the utility of this technique in reducing sampling error to identify SIM.

Barrett Esophagus↗
PubMed2000

Stereotactic core-needle breast biopsy by surgeons: minimum 2-year follow-up of benign lesions.

OBJECTIVE: To evaluate the reliability of stereotactic core-needle breast biopsy (SCNB) performed by surgeons to detect histologically benign tissue. SUMMARY BACKGROUND DATA: Stereotactic core-needle breast biopsy is widely used to obtain tissue for definitive pathologic diagnosis of mammographically suspicious breast lesions. It has an incidence of malignancy detection similar to that of open biopsy. The potential for sampling error is a concern. Minimal data regarding follow-up and failure rate are available, especially from series performed exclusively by surgeons. METHODS: Pertinent medical records of all patients who underwent SCNB between April 1995 and October 1997 were reviewed. Breast lesions were classified by mammographic Breast Imaging-Reporting and Data Systems (BI-RADS) categories before SCNB. Benign biopsy specimens were classified as nonproliferative or proliferative. Malignant lesions and those with atypical histopathology by SCNB were excluded from this analysis. All lesions initially reported as benign were followed up mammographically for at least 2 years for any suspicious change requiring repeat biopsy. RESULTS: During the 31-month period, SCNB was performed on 694 lesions in 619 patients. Histologic evidence of malignancy was found in 112 lesions (16%). The initial histologic diagnosis for the remaining 582 lesions was benign. Four hundred lesions were available for follow-up; of these, 373 (93%) were mammographically categorized as BI-RADS 3 (probably benign) or 4 (suspicious). Three hundred forty-three lesions were categorized as nonproliferative and 151 as proliferative (94 had combined nonproliferative and proliferative histology). Follow-up ranged from 24 to 48 months (mean 33 months). During the follow-up period, 87 lesions (21.8%) underwent either image-guided or open biopsy. At the time of follow-up rebiopsy, ductal carcinoma in situ was found in four lesions and infiltrating ductal carcinoma was found in one, for an overall false-negative rate of 4.3% (5/117) and a negative predictive value of 98.8% (395/400). For the five false-negative cases, the interval from initial SCNB to definitive diagnosis ranged from 7 to 36 months. No correlation was found between the type of initial histopathology and development of malignancy. CONCLUSIONS: These results support SCNB as an alternative to open biopsy and show the reliability of SCNB when benign pathology is obtained. However, given the possibility of sampling error and the nature of breast disease, close mammographic and clinical follow-up is necessary. The false-negative rate and negative predictive value in this series compare favorably with those in other reports, supporting the fact that surgeons can confidently use SCNB in the evaluation and treatment of breast disease.

Adult↗
PubMed2002

Adenocarcinoma of the cervix.

BACKGROUND: The current study examines 1) the sensitivity of detection of invasive adenocarcinoma of the cervix in a routine cervical screening service, and 2) the frequency in smears of cytologic criteria previously found to be useful in diagnosis. METHODS: Data on women with diagnoses of adenocarcinoma of the cervix accessioned at the Western Australian Cervical Cytology Registry during the period 1993-1998 were examined, where smears had been reported by Western Diagnostic Pathology within three years of the biopsy diagnosis. Smears and biopsy material were reviewed. RESULTS: Thirty-six smears from 24 women were reviewed. Of those, 58.3% had been reported as a possible or definite high grade epithelial abnormality (HGEA). On review it was thought that this could be improved to 77.8%. The screening or diagnostic error was thus 19.4% and the sampling error 22.2%. The likelihood of an individual woman receiving a report of a possible or definite HGEA in the three years before biopsy was 83.3%. In retrospect this could have been improved to 91.7%. Heavy bloodstaining with abundant abnormal glandular epithelium (14 smears) and small three-dimensional or papillary clusters (16 smears) were the most frequent clues to invasion. Tumor necrosis/diathesis was present in eight smears, but easily seen in only four, while marked nuclear pleomorphism and macronucleoli were seen in three and one smears respectively. In cases with a discrepancy between the initial and the review findings, very small amounts of abnormal material (three smears), a resemblance to endometrial cells (one smear), and an unusual appearance of folded monolayered sheets (three smears) contributed to the difficulty of diagnosis. CONCLUSIONS: There were significant sampling and screening/diagnostic errors (22.2% and 19.4%, respectively). Screening and diagnostic errors could perhaps be reduced by a greater awareness of the range of cytologic changes, but these may be subtle. Heavy bloodstaining with abundant abnormal glandular material may be a useful clue to invasive, rather than in situ, adenocarcinoma, even in the absence of tumor diathesis or fully malignant nuclear criteria.

Adenoma↗
PubMed1995

The Maastricht protocol for the measurement of body composition and energy expenditure with labeled water.

An update of practical aspects of the use of labeled water for the measurement of total body water (TBW) and energy expenditure (EE) is presented as applied in Maastricht, The Netherlands. We use a 10-hour equilibration period. The isotopes for the measurement of TBW and EE are routinely administered, after collecting a background urine sample, as a last consumption before the night. Our data show an underestimate of TBW measured with isotope dilution after 4 hours (in the morning), a discrepancy which increases with the size of TBW. No such relation and no significant differences were found after 10-hour (overnight) equilibration. The ratio between the dilution space for deuterium and oxygen-18 is higher than the earlier figure of 1.03, especially in adult subjects with a high body fat content. For an observation period of EE over two weeks, samples from the second and the last voiding on the first, mid, and last day of the observation period are collected. Differences in EE calculated from morning and evening samples within the first and second week allow detection of sampling errors and if so, samples are excluded from the final calculation. Differences of EE between weeks 1 and 2 allow a check for the consistency of the subjects' physical activity level and usually fall within 10% of the average EE over the total observation interval.

Body Composition↗
PubMed1996

Standard error and sample size determination for estimation of probabilities based on a test variable.

A method of sample size determination for estimation of probabilities based on a test variable is presented. Applications to estimation of sensitivity and specificity of medical tests are the focus of this research, although the methods can be applied to other areas of study such as engineering reliability. Examples are given for determining sample sizes required for the classification of patients with cutaneous lupus erythematosus based on the incidence of several markers. In this example, the test variable is the number of markers present. The methodology employs a weighted average of model-based and non-model-based estimates of the probability with the weights determined by the closeness to or the confidence in the given model. Formulas and charts required for determining sample size are provided for test variables that can be modeled by the binomial, Poisson, or normal distributions, i.e., for the most commonly encountered distributions for counting events (binomial and Poisson) and for measurements (normal). However, the methods given can be applied to any distribution, including multivariate. Especially when relatively small probabilities (the rare events) are being estimated, the techniques provided assistance in safeguarding against undersampling brought on by unwarranted confidence in a test variable distribution and against oversampling required for high accuracy in non-model-based probability estimators.

Epidemiologic Methods↗
PubMed2002

Estimation of second order rate constants using chemometric methods with kinetic constraints.

Several methods are described for determining rate constants for second order reactions of the form U + V --> W using chemometrics and hard modelling to analyse UV absorption spectroscopic data, where all species absorb with comparable concentrations and extinctions. An interesting feature of this type of reaction is that the number of steps in the reaction is less than the number of absorbing species, resulting in a rank-deficient response matrix. This can cause problems when using some of the methods described in the literature. The approaches discussed in the paper depend, in part, on what knowledge is available about the system, including the spectra of the reactants and product, the initial concentrations and the exact kinetics. Sometimes some of this information may not be available or may be hard to estimate. Five groups of methods are discussed, namely use of multiple linear regression to obtain concentration profiles and fit kinetics information, rank augmentation using multiple batch runs, difference spectra based approaches, mixed spectral approaches which treat the reaction as two independent pseudospecies, and principal components regression. Two datasets are simulated, one where the spectra are quite different and the other where the spectrum of one reactant and the product share a high degree of overlap. Three sources of error are considered, namely sampling error, instrumental noise and errors in initial concentrations. The relative merits of each method are discussed.

Journal Article↗
PubMed1978

The importance of beta, the type II error and sample size in the design and interpretation of the randomized control trial. Survey of 71 "negative" trials.

Seventy-one "negative" randomized control trials were re-examined to determine if the investigators had studied large enough samples to give a high probability (greater than 0.90) of detecting a 25 per cent and 50 per cent therapeutic improvement in the response. Sixty-seven of the trials had a greater than 10 per cent risk of missing a true 25 per cent therapeutic improvement, and with the same risk, 50 of the trials could have missed a 50 per cent improvement. Estimates of 90 per cent confidence intervals for the true improvement in each trial showed that in 57 of these "negative" trials, a potential 25 per cent improvement was possible, and 34 of the trials showed a potential 50 per cent improvement. Many of the therapies labeled as "no different from control" in trials using inadequate samples have not received a fair test. Concern for the probability of missing an important therapeutic improvement because of small sample sizes deserves more attention in the planning of clinical trials.

Clinical Trials as Topic↗