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A study of mean glandular dose during diagnostic mammography in Malaysia and some of the factors affecting it

Jamal N, Ng KH, McLean D

Br J Radiol, 2003 Apr;76(904):238-45.
PMID: 12711643

The primary objective of this study was to determine the mean glandular dose (MGD) during diagnostic mammography in Malaysia. The secondary objective was to evaluate some of the factors affecting MGD. A survey of standard MGD was performed, based upon quality control records for the period October 1999 to August 2001. This covered 30 mammography units from 9 manufacturers. MGD was also measured for a series of patients attending mammography examinations at three other mammography units. MGD per film was estimated from recorded radiographic factors, the compressed breast thickness (CBT) and X-ray unit calibration data. MGD per woman was calculated by summing the MGDs for all films, and averaging it over both breasts. 300 women drawn equally from three major ethnic groups, namely Malay, Chinese and Indian, took part in the study. The difference of MGD per woman between ethnic groups was tested for significance using non-parametric Kruskal-Wallis and median tests. The factors affecting MGD per woman were tested for significance using a multivariate analysis of variance. The MGD for the phantom was 1.23 mGy (range 0.22-2.39 mGy) while the mean patient based MGD per film was 1.54 mGy and 1.82 mGy for the craniocaudal and mediolateral oblique views, respectively. The mean MGD per woman was 3.37 mGy. It was also found that there is no significant difference in MGD per woman among the ethnic groups (p>0.05, Kruskal-Wallis test). However, on the multivariate test two factors, namely half value layer of the X-ray beam and (CBT), had a significant effect on MGD per woman (p<0.05). No significant relationships were seen between MGD per woman with respect to ethnicity, body mass index or age.
Mammographic breast glandularity in Malaysian women: data derived from radiography

Jamal N, Ng KH, McLean D, Looi LM, Moosa F

AJR Am J Roentgenol, 2004 Mar;182(3):713-7.
PMID: 14975974

This study was undertaken to estimate mammographic breast glandularity in Malaysian women from radiographic data.
Refining clinical phenotypes by contrasting ethnically different populations with schizophrenia from Australia, India and Sarawak

McLean D, John S, Barrett R, McGrath J, Loa P, Thara R, et al.

Psychiatry Res, 2012 Apr 30;196(2-3):194-200.
PMID: 22401968 DOI: 10.1016/j.psychres.2011.12.027

We contrasted demographic and clinical characteristics in transethnic schizophrenia populations from Australia (n=821), India (n=520) and Sarawak, Malaysia (n=298) and proposed cultural explanations for identified site differences. From these we aimed to identify candidate variables free from significant cultural confounding that are hence suitable for inclusion in genetic analyses. We observed five phenomena: (1) more individuals were living alone in Australia than India or Sarawak; (2) drug use was lower in India than Australia or Sarawak; (3) duration of untreated psychosis (DUP) was longer in India than Australia or Sarawak; (4) the rate of schizoaffective disorder was lower in India than Australia or Sarawak; and (5) age at psychosis onset (AAO) was older in Sarawak than Australia or India. We suggest that site differences for living arrangements, drug use and DUP are culturally confounded. The schizoaffective site difference likely results from measurement bias. The AAO site difference, however, has no obvious cultural or measurement bias explanation. Therefore, this may be an ideal candidate for use in genetic studies, given that genetic variants affecting AAO have already been proposed.
Quantitative assessment of breast density from digitized mammograms into Tabar's patterns

Jamal N, Ng KH, Looi LM, McLean D, Zulfiqar A, Tan SP, et al.

Phys Med Biol, 2006 Nov 21;51(22):5843-57.
PMID: 17068368

We describe a semi-automated technique for the quantitative assessment of breast density from digitized mammograms in comparison with patterns suggested by Tabar. It was developed using the MATLAB-based graphical user interface applications. It is based on an interactive thresholding method, after a short automated method that shows the fibroglandular tissue area, breast area and breast density each time new thresholds are placed on the image. The breast density is taken as a percentage of the fibroglandular tissue to the breast tissue areas. It was tested in four different ways, namely by examining: (i) correlation of the quantitative assessment results with subjective classification, (ii) classification performance using the quantitative assessment technique, (iii) interobserver agreement and (iv) intraobserver agreement. The results of the quantitative assessment correlated well (r2 = 0.92) with the subjective Tabar patterns classified by the radiologist (correctly classified 83% of digitized mammograms). The average kappa coefficient for the agreement between the readers was 0.63. This indicated moderate agreement between the three observers in classifying breast density using the quantitative assessment technique. The kappa coefficient of 0.75 for intraobserver agreement reflected good agreement between two sets of readings. The technique may be useful as a supplement to the radiologist's assessment in classifying mammograms into Tabar's pattern associated with breast cancer risk.
Fulltext Comparing schizophrenia symptoms in the Iban of Sarawak with other populations to elucidate clinical heterogeneity

McLean D, Barrett R, Loa P, Thara R, John S, McGrath J, et al.

Asia Pac Psychiatry, 2015 Mar;7(1):36-44.
PMID: 24038814 DOI: 10.1111/appy.12093

INTRODUCTION: The symptom profile of schizophrenia can vary between ethnic groups. We explored selected symptom variables previously reported to be characteristic of schizophrenia in the Iban of Sarawak in transethnic populations from Australia, India, and Sarawak, Malaysia. We tested site differences to confirm previous research, and to explore implications of differences across populations for future investigations.
METHODS: We recruited schizophrenia samples in Australia (n = 609), India (n = 310) and Sarawak (n = 205) primarily for the purposes of genetic studies. We analyzed seven identified variables and their relationship to site using logistic regression, including: global delusions, bizarre delusions, thought broadcast/insertion/withdrawal delusions, global hallucinations, auditory hallucinations, disorganized behavior, and prodromal duration.
RESULTS: We identified a distinct symptom profile in our Sarawak sample. Specifically, the Iban exhibit: low frequency of thought broadcast/insertion/withdrawal delusions, high frequency of auditory hallucinations and disorganized behavior, with a comparatively short prodrome when compared with Australian and Indian populations.
DISCUSSION: Understanding between-site variation in symptom profile may complement future transethnic genetic studies, and provide important clues as to the nature of differing schizophrenia expression across ethnically distinct groups. A comprehensive approach to subtyping schizophrenia is warranted, utilizing comprehensively ascertained transethnic samples to inform both schizophrenia genetics and nosology.
Fulltext DSM-IV "criterion A" schizophrenia symptoms across ethnically different populations: evidence for differing psychotic symptom content or structural organization?

McLean D, Thara R, John S, Barrett R, Loa P, McGrath J, et al.

Cult Med Psychiatry, 2014 Sep;38(3):408-26.
PMID: 24981830 DOI: 10.1007/s11013-014-9385-8

There is significant variation in the expression of schizophrenia across ethnically different populations, and the optimal structural and diagnostic representation of schizophrenia are contested. We contrasted both lifetime frequencies of DSM-IV criterion A (the core symptom criterion of the internationally recognized DSM classification system) symptoms and types/content of delusions and hallucinations in transethnic schizophrenia populations from Australia (n = 776), India (n = 504) and Sarawak, Malaysia (n = 259), to elucidate clinical heterogeneity. Differences in both criterion A symptom composition and symptom content were apparent. Indian individuals with schizophrenia reported negative symptoms more frequently than other sites, whereas individuals from Sarawak reported disorganized symptoms more frequently. Delusions of control and thought broadcast, insertion, or withdrawal were less frequent in Sarawak than Australia. Curiously, a subgroup of 20 Indian individuals with schizophrenia reported no lifetime delusions or hallucinations. These findings potentially challenge the long-held view in psychiatry that schizophrenia is fundamentally similar across cultural groups, with differences in only the content of psychotic symptoms, but equivalence in structural form.
Global status and conservation potential of reef sharks

MacNeil MA, Chapman DD, Heupel M, Simpfendorfer CA, Heithaus M, Meekan M, et al.

Nature, 2020 07;583(7818):801-806.
PMID: 32699418 DOI: 10.1038/s41586-020-2519-y

Decades of overexploitation have devastated shark populations, leaving considerable doubt as to their ecological status1,2. Yet much of what is known about sharks has been inferred from catch records in industrial fisheries, whereas far less information is available about sharks that live in coastal habitats3. Here we address this knowledge gap using data from more than 15,000 standardized baited remote underwater video stations that were deployed on 371 reefs in 58 nations to estimate the conservation status of reef sharks globally. Our results reveal the profound impact that fishing has had on reef shark populations: we observed no sharks on almost 20% of the surveyed reefs. Reef sharks were almost completely absent from reefs in several nations, and shark depletion was strongly related to socio-economic conditions such as the size and proximity of the nearest market, poor governance and the density of the human population. However, opportunities for the conservation of reef sharks remain: shark sanctuaries, closed areas, catch limits and an absence of gillnets and longlines were associated with a substantially higher relative abundance of reef sharks. These results reveal several policy pathways for the restoration and management of reef shark populations, from direct top-down management of fishing to indirect improvement of governance conditions. Reef shark populations will only have a high chance of recovery by engaging key socio-economic aspects of tropical fisheries.
Author Correction: Global status and conservation potential of reef sharks

MacNeil MA, Chapman DD, Heupel M, Simpfendorfer CA, Heithaus M, Meekan M, et al.

Nature, 2020 09;585(7825):E11.
PMID: 32848253 DOI: 10.1038/s41586-020-2692-z

An Amendment to this paper has been published and can be accessed via a link at the top of the paper.
Widespread diversity deficits of coral reef sharks and rays

Simpfendorfer CA, Heithaus MR, Heupel MR, MacNeil MA, Meekan M, Harvey E, et al.

Science, 2023 Jun 16;380(6650):1155-1160.
PMID: 37319199 DOI: 10.1126/science.ade4884

A global survey of coral reefs reveals that overfishing is driving resident shark species toward extinction, causing diversity deficits in reef elasmobranch (shark and ray) assemblages. Our species-level analysis revealed global declines of 60 to 73% for five common resident reef shark species and that individual shark species were not detected at 34 to 47% of surveyed reefs. As reefs become more shark-depleted, rays begin to dominate assemblages. Shark-dominated assemblages persist in wealthy nations with strong governance and in highly protected areas, whereas poverty, weak governance, and a lack of shark management are associated with depauperate assemblages mainly composed of rays. Without action to address these diversity deficits, loss of ecological function and ecosystem services will increasingly affect human communities.