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L Irwig

Publications and source records attributed to L Irwig.

At least 19 recordsLinked to original sources
PubMed2006

Impact of privacy legislation on the number and characteristics of people who are recruited for research: a randomised controlled trial.

BACKGROUND: Privacy laws have recently created restrictions on how researchers can approach study participants. METHOD: In a randomised trial of 152 patients, 50-74 years old, in a family practice, 60 were randomly selected to opt-out and 92 to opt-in methods. Patients were sent an introductory letter by their doctor in two phases, opt-out before and opt-in after introduction of the new Privacy Legislation in December 2001. Opt-out patients were contacted by researchers. Opt-in patients were contacted if patients responded by email, free telephone number or a reply-paid card. RESULTS: Opt-in recruited fewer patients (47%; 43/92) after invitation compared with opt-out (67%; 40/60); (-20%; [-4% to -36%]). No proportional difference in recruitment was found between opt-in and opt-out groups varied by age, sex or socioeconomic status. The opt-in group had significantly more people in active decision-making roles (+30%; [10% to 50%]; p = 0.003). Non-significant trends were observed towards opt-in being less likely to include people with lower education (-11.8%; [-30% to 6.4%]; p = 0.13) and people who were not screened (-19.1%; [-40.1% to 1.9%]; p = 0.08). Opt-in was more likely to recruit people with a family history of colorectal cancer (+12.7%; [-2.8%, 28.2%]; p = 0.12). CONCLUSIONS: The number of participants required to be approached was markedly increased in opt-in recruitment. Existing participants (eg, screening attendees) with a vested interest such as increased risk, and those preferring an active role in health decision making and with less education were likely to be recruited in opt-in. Research costs and generalisability are affected by implementing privacy legislation.

Age Factors↗
PubMed2005

Meta-analysis of sentinel node imprint cytology in breast cancer.

BACKGROUND: Intraoperative diagnosis of breast cancer metastases in axillary sentinel nodes is desirable to avoid a second operation for lymphadenectomy. Imprint or touch-preparation cytology is a popular technique that has high specificity and a wide range of sensitivity. METHODS: A systematic search of electronic databases was performed. Included articles were assessed for methodological and reporting quality. Random-effects model pooled estimates of sensitivity and specificity were calculated. Single-variable and multivariable meta-regression analyses were performed for predictors of sensitivity. RESULTS: Thirty-one studies were included; all were of good methodological quality but reporting quality varied. Pooled sensitivity of imprint cytology was 63 (95 per cent confidence interval (c.i.) 57 to 69) per cent and specificity was 99 (95 per cent c.i. 98 to 99) per cent. Pooled sensitivity for macrometastases was 81 per cent and that for micrometastases 22 per cent. Mean or median primary tumour size (P = 0.004), the prevalence of metastases (P = 0.103) and the proportion of micrometastases (P = 0.022) were significant risk factors in single-variable meta-regression analysis. Only the proportion of micrometastases remained significant in multivariable analysis. Frozen sectioning had better sensitivity than imprint cytology in three of four direct comparisons. CONCLUSION: Imprint cytology is simple and rapid, and has good sensitivity for macrometastases. The significance of poor sensitivity for micrometastases will be determined by trials investigating their natural history.

Breast↗
PubMed2005

Florence-Sydney Breast Biopsy Study: sensitivity of ultrasound-guided versus freehand fine needle biopsy of palpable breast cancer.

BACKGROUND: Fine needle aspiration biopsy (FNAB) is widely used in the diagnosis of breast cancer. It is unknown whether, for palpable cancers, ultrasound-guided FNAB is more accurate than freehand FNAB, and practice varies between physicians, services and countries. METHODS: From consecutive women attending a major cancer centre in Florence, we prospectively recruited subjects who had a definitely palpable lump which was solid on ultrasound and suspicious of malignancy (n = 102). All subjects were investigated using both ultrasound-guided and freehand FNAB (one aspirate with each method). Radiologists skilled in both sampling techniques performed all clinical examinations and aspirations, and for each subject the same radiologist obtained both FNAB samples. Sequence of aspiration method was randomised. Cytological interpretation was blinded to method of sampling. Comparative sensitivity (and insufficiency) for FNAB using the two methods was calculated in all cancers (n = 97). RESULTS: Ultrasound-guided FNAB resulted in 13.6% (5-22%) less insufficient aspirates than freehand FNAB (chi2 = 7.58; p = 0.006). When insufficient aspirates are included and considered as negative, ultrasound-guided FNAB has a 14.6% (5.8-23%) or a 16.5% (7.6-25.4%) significantly better sensitivity than freehand FNAB (for cytology 3-5 positive or cytology 4-5 positive respectively). When insufficient aspirates are excluded from the analysis, ultrasound-guided FNAB has a 1.4% (-1.2 to 3.9%) or a 2.6% (-2.5 to 7.8%) higher sensitivity than freehand FNAB (for cytology 3-5 positive or cytology 4-5 positive respectively) but this difference in the sensitivity of the two methods is not statistically significant. CONCLUSION: Our data suggest that ultrasound-guided FNAB has better sensitivity than freehand FNAB in palpable breast cancer, which is predominantly an effect of a significant reduction in insufficient aspirates, but in part an effect of 'upgrading' cytological classification of cancers.

Adult↗
PubMed2004

New technologies in screening for breast cancer: a systematic review of their accuracy.

We systematically reviewed the literature on the accuracy of new technologies proposed for breast cancer screening. Four potential tests were identified (ultrasound, magnetic resonance imaging (MRI), full-field digital mammography (FFDM), and computer-aided detection (CAD)) for which primary studies met quality and applicability criteria and provided adequate data on test accuracy. These technologies have been assessed in cross-sectional studies of test accuracy where the new test is compared to mammography. Ultrasound, used as an adjunct to mammography in women with radiologically dense breasts, detects additional cancers and causes additional false positives. Magnetic resonance imaging may have a better sensitivity (but lower specificity) than mammography in selected high-risk women, but studies of this technology included small number of cancers. Computer-aided detection may enhance the sensitivity of mammography and warrants further evaluation in large prospective trials. One study of FFDM suggests that it may identify some cancers not identified on conventional mammography and may result in a lower recall rate. The evidence is currently insufficient to support the use of any of these new technologies in population screening, but would support further evaluation.

Breast Neoplasms↗
PubMed2004

Exfoliative cytology as a diagnostic test for basal cell carcinoma: a meta-analysis.

BACKGROUND: Exfoliative cytology is only occasionally used in clinical practice to diagnose basal cell carcinoma (BCC). OBJECTIVES: To systematically review the literature examining exfoliative cytology as a diagnostic tool for BCC and to meta-analytically summarize the accuracy of this test. METHODS: Diagnostic test meta-analysis. A computerized database search was made of MEDLINE (1966-2000) and EMBASE (1950-2000) using appropriately indexed terms. Hand searches of relevant journals were made. Bibliographies of relevant articles were further explored. Histopathology was used as the reference standard. A summary receiver-operating characteristic curve analysis was performed using the statistical package Meta-Test version 0.6 (J. Lau, New England Medical Center, Boston, MA, U.S.A., 1997). RESULTS: Eight primary studies (seven English language and one Italian language) fulfilled the inclusion criteria. The pooled sample included 1261 BCCs. These studies varied greatly in methodological quality and were, in general, poor. A meta-analysis showed the pooled sensitivity to be high at 97%[95% confidence interval (CI) 94-99]. Consequently, only 3% of BCCs included were misdiagnosed as non-BCC by cytology. The corresponding pooled specificity was 86% (95% CI 80-91). CONCLUSIONS: Exfoliative cytology probably has a high diagnostic accuracy for BCC. However, large, better designed and better reported studies are needed to ascertain the true accuracy of this technique. In the interim, this test should be considered in specific subgroups of patients in whom even a 2-mm punch biopsy may be considered inappropriate, e.g. a cosmetically sensitive site in a young person. Similarly, it should be considered when a BCC is to be treated without a diagnostic biopsy being taken, e.g. with cryotherapy.

Basal Cell Carcinoma↗
PubMed2003

The contribution of work-up or additional views to the accuracy of diagnostic mammography.

This study examines the influence of work-up on the accuracy of diagnostic mammography in symptomatic women. Subjects were sampled from all women consecutively attending a symptomatic breast clinic and aged 25-55 years (240 women shown to have breast cancer and 240 age-matched women shown not to have cancer). Mammography films were prospectively reported by two radiologists independently of each other and in a blinded manner using two phases of film reading: initially only baseline films were read, then mammography was re-read with work-up films. The accuracy of reporting mammography with and without work-up was compared using sensitivity and specificity, likelihood ratios, and receiver operating characteristic (ROC) curves. Reporting the mammogram with work-up (compared to without any work-up films) improved sensitivity (75.3% vs 69.0%, P=0.059) for one radiologist, with a non-significant gain in specificity (84.5% vs 79.4%, P=0.38). For the other radiologist, it resulted in a non-significant decrease in sensitivity (79.5% vs 83.7%, P=0.14) with a significant increase in specificity (85.6% vs 61.9%, P=0.00001). ROC curves for both radiologists showed that reporting mammography with work-up resulted in significant improvement (4.5% for R1, 6.8% for R2) in overall test accuracy. Our findings support the use of work-up mammography in the diagnostic setting.

Adult↗
PubMed2002

Serological diagnosis of pertussis: evaluation of IgA against whole cell and specific Bordetella pertussis antigens as markers of recent infection.

In Australia, notification of pertussis cases in older children or adults has increased significantly in recent years. In most cases, laboratory diagnosis is based only on a positive serological test for IgA antibody against whole cell Bordetella pertussis. During a 3-month period, 318 consecutive sera submitted for diagnosis of pertussis were tested for IgA antibody against whole cell (WC) sonicated B. pertussis, pertussis toxin (PT), filamentous haemagglutinin (FHA) and pertactin (PRN). Results of one or more of these tests were positive in sera from 175 subjects and clinical information was obtained by telephone interview from 90 subjects. Using a clinical case definition as the reference standard, the sensitivities of the four IgA assays were variable but quite low (24-64%), but the specificities were high (93-98%). For diagnosis of pertussis in subjects with a compatible clinical illness, these and other findings support the use of serological testing for IgA antibody.

Adolescent↗
PubMed2002

Accuracy of combined breast imaging in young women.

This is a study of the accuracy of combined breast imaging (mammography and ultrasound) in young women with breast symptoms. We performed an appraisal of the literature, and improved our study design by avoiding biases identified in published work. Our study presents the sensitivity and specificity of mammography and breast ultrasound, individually and in combination, using different thresholds for categorizing test results, in a population of consecutive women. We show that combining the two imaging tests does improve sensitivity without significantly reducing test specificity. However, the number of additional cancers correctly identified using combined imaging, relative to the number of false positives, is highly dependent on breast cancer prevalence.

Journal Article↗
PubMed2002

The comparative sensitivity of mammography and ultrasound in women with breast symptoms: an age-specific analysis.

Despite its importance for clinical policy, there is little research on the age at which ultrasound or mammography is the preferred initial diagnostic test in women with breast symptoms. We analysed data from a series of 3799 consecutively presenting cancers. The overall sensitivity was 77.6% for mammography and 80.5% for ultrasound. Sensitivity increased with age in both mammography and ultrasound, though more steeply for mammography. In the 975 women who had both tests, ultrasound had a higher sensitivity than mammography in women younger than 62 years of age, whereas mammography had a higher sensitivity than ultrasound in women older than 62 years. However, if the test results of the 2393 women who had mammography only are compared with the ultrasound results of the 975 women who had both tests, the 'cross-over' age at which the sensitivity of the two tests is equal occurs at the earlier age of 48 years. The presence of a palpable finding increases the sensitivity of ultrasound but does not influence the sensitivity of mammography.

Journal Article↗
PubMed2002

Evidence relevant to the investigation of breast symptoms: the triple test.

This paper reviews and summarises evidence on the investigation of breast symptoms based on triple testing. The triple test (where any component is positive) has a sensitivity of 99.6%, a specificity of 62%, a likelihood ratio of 2.62 for a positive result, and a likelihood ratio of 0.006 for a negative result. We present measures of test accuracy for the components of the triple test that allow easy estimation of the probability of breast cancer in symptomatic women, given any possible combination of results.

Journal Article↗
PubMed2002

Cancer screening.

"Screening is the systematic application of a test or inquiry, to identify individuals at sufficient risk of a specific disorder to benefit from further investigation or direct preventive action, among persons who have not sought medical attention on account of symptoms of that disorder."

Adult↗
PubMed2001

Estimating the number needed to treat (NNT) index when the data are subject to error.

The number needed to treat (NNT) index has been proposed as a clinically useful measure to assess the results of randomized trials and other clinical studies. In its usual form, NNT indicates the expected number of patients who must be treated with an experimental therapy in order to prevent one adverse event, compared to the expected event rates under the control therapy. It can be formulated as a function of the proportions of patients who respond to treatment by more than a certain amount, the clinically important difference. We may also wish to evaluate two group studies comparing treatment and control responses, and to consider net benefit from treatment (by also allowing for individuals who deteriorate as well as those who respond positively). In this paper, we investigate the effect on NNT caused by measurement errors in continuous outcome measures. Such errors can lead to bias in the estimated proportions of subjects with clinically important responses, and hence bias the associated values of NNT. General expressions for the bias are derived, and enumerated for typical scenarios. For many situations, reliability of 80 per cent or more in the observations is required to restrict the bias to tolerable levels.

Bias↗
PubMed2001

A comparison of methods to detect publication bias in meta-analysis.

Meta-analyses are subject to bias for many of reasons, including publication bias. Asymmetry in a funnel plot of study size against treatment effect is often used to identify such bias. We compare the performance of three simple methods of testing for bias: the rank correlation method; a simple linear regression of the standardized estimate of treatment effect on the precision of the estimate; and a regression of the treatment effect on sample size. The tests are applied to simulated meta-analyses in the presence and absence of publication bias. Both one-sided and two-sided censoring of studies based on statistical significance was used. The results indicate that none of the tests performs consistently well. Test performance varied with the magnitude of the true treatment effect, distribution of study size and whether a one- or two-tailed significance test was employed. Overall, the power of the tests was low when the number of studies per meta-analysis was close to that often observed in practice. Tests that showed the highest power also had type I error rates higher than the nominal level. Based on the empirical type I error rates, a regression of treatment effect on sample size, weighted by the inverse of the variance of the logit of the pooled proportion (using the marginal total) is the preferred method.

Computer Simulation↗
PubMed2000

Screening for colorectal cancer using the faecal occult blood test, hemoccult.

BACKGROUND: Colorectal cancer is a leading cause of illness and death in the Western world. In Australia, the United Kingdom and the United States, it is the second commonest cancer for women after breast cancer (age-standardised incidence 22-33 per 100,000), and men after prostate or lung cancer (age-standardised incidence 31-47 per 100,000) (Jeffs et al, 1996; Parkin et al, 1992). Just under half of all persons affected will die from their disease (Jeffs et al, 1996; Parkin et al, 1992) The human and financial costs of this disease have prompted considerable research efforts to evaluate the ability of screening tests to detect the cancer at an early curable stage. Tests which have been considered for screening include faecal occult blood tests, sigmoidoscopy and colonoscopy. OBJECTIVES: To determine whether screening for colorectal cancer using the faecal occult blood test, Hemoccult reduces colorectal cancer mortality and to consider the benefits and harms of screening. SEARCH STRATEGY: Published and unpublished data for this review were identified by: * retrieving studies included in a systematic review conducted by some of the authors in 1995, * searches of MEDLINE, Current Contents and the Cochrane Controlled Trials Register, * writing to trial lists. SELECTION CRITERIA: All controlled trials of screening for colorectal cancer using Hemoccult were eligible for inclusion in the review. DATA COLLECTION AND ANALYSIS: Data from the trials were independently extracted by two authors. Data analysis was performed using the group subjects were randomised to ('intention to screen'), whether or not they were ever screened. To estimate the effect of Hemoccult screening on colorectal cancer mortality, we calculated relative risks and risk differences for each trial, and then overall, using fixed and random effects models and tested for heterogeneity of effects. We calculated summary measures of effect including all trials and also for just the randomised controlled trials. We also calculated a summary measure of effect, adjusted for attendance at screening in each trial (not shown in Meta-view). MAIN RESULTS: Meta-analysis of mortality results from the randomised controlled trials shows that those allocated to screening had a reduction in colorectal cancer mortality of 16% (RR 0.84, CI: 0.77-0.93). When adjusted for screening attendance in the individual studies, the mortality reduction is 23% (RR 0.77, CI: 0.57-0.89). Overall, if 10 000 people were offered a biennial Hemoccult screening program and two-thirds attended for at least one Hemoccult test, there would be 8.5 deaths (CI: 3.6-13.5) from colorectal cancer prevented over 10 years. However, the screening program would also result in 2 800 participants having at least one colonoscopy, if screening harms from the Minnesota trial are considered, and there would be 3.4 colonoscopy complications (perforation or haemorrhage). If screening harms from the Gothenburg trial are considered, approximately 600 participants would need at least one sigmoidoscopy and double contrast barium enema, resulting in 1.8 perforations or haemorrhages. REVIEWER'S CONCLUSIONS: Screening benefits include reduction in colorectal cancer mortality, possible reduction in cancer incidence through detection and removal of colorectal adenomas and potentially, treatment of early colorectal cancers may involve less invasive surgery. Harmful effects of screening include the physical complications of colonoscopy, disruption to lifestyle, stress and discomfort of testing and investigations, and the anxiety caused by falsely positive screening tests. Although screening benefits are likely to outweigh harms for populations at increased risk of colorectal cancer, we need more information about the harmful effects of screening, the community's responses to screening and screening costs for different health care systems before widespread screening can be recommended.

Colorectal Neoplasms↗
PubMed2000

Reliability of DMSA for the diagnosis of renal parenchymal abnormality in children.

The objective of this study was to evaluate the variability of technetium-99m dimercaptosuccinic acid (DMSA) scintigraphy interpretation by four nuclear medicine physicians for the diagnosis of renal parenchymal abnormality in children, and to compare variability among three different DMSA methods in clinical use: planar alone, single-photon emission tomography (SPET) alone, and planar with SPET. One hundred consecutive DMSA studies were independently interpreted 3 times by four participating nuclear medicine specialists from different departments and in random order. All scans were classified by the presence or absence of renal parenchymal abnormality using the modified four-level grading system of Goldraich. Indices of agreement were the percentage of agreement and the kappa statistic. Disagreement was analysed using children, kidneys and kidney zones (three zones per kidney). Using patients as the unit of analysis, agreement for planar and planar with SPET methods was 87%-88% (kappa 0.74) for the normal-abnormal scan classification. The corresponding agreement value for the SPET alone method was 78% (kappa 0.56). Similarly, substantial disagreement (disagreement > or = 2 categories) occurred in 2.5% and 1.3% of comparisons between observers for planar alone and planar with SPET, respectively, but in 5.2% of comparisons for SPET alone. These results did not vary appreciably whether interpretation of patients, kidneys or kidney zones was compared. It is concluded that the four experienced nuclear medicine physicians showed substantial agreement in the interpretation of planar alone and planar with SPET DMSA scintigraphic images. Interpretation of SPET DMSA images, without planar images, was significantly more variable than interpretation using the two other methods, disagreement occurring in more than 20% of comparisons. SPET DMSA scintigraphy, when used without planar images, does not provide a firm basis for clinical decision making in the care of children who may have renal damage. There is no apparent benefit of reduced variability from the extra provision of SPET data to nuclear medicine physicians who already have planar images.

Child↗