Samuel William David Merriel

Dr. Samuel William David Merriel

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Research Focus & Metrics

Academic Career Length

12Years (2015-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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7 February 2022 in BMC Medicine
Verified
Journal Article
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SMSamuel Merriel
Samuel Merriel
LPLucy Pocock
Lucy Pocock
EGEmma Gilbert
Emma Gilbert
SCSam Creavin
Sam Creavin
FWFiona M. Walter
Fiona M. Walter
WHWillie Hamilton
Willie Hamilton
Background: Prostate-specific antigen (PSA) is a commonly used test to detect prostate cancer. Attention has mostly focused on the use of PSA in screening asymptomatic patients, but the diagnostic accuracy of PSA for prostate cancer in patients with symptoms is less well understood.Methods: A systematic database search was conducted of Medline, EMBASE, Web of Science, and the Cochrane library. Studies reporting the diagnostic accuracy of PSA for prostate cancer in patients with symptoms were included. Two investigators independently assessed the titles and abstracts of all database search hits and full texts of potentially relevant studies against the inclusion criteria, and data extracted into a proforma. Study quality was assessed using the QUADAS-2 tool by two investigators independently. Summary estimates of diagnostic accuracy were calculated with meta-analysis using bivariate mixed effects regression.Results: Five hundred sixty-three search hits were assessed by title and abstract after de-duplication, with 75 full text papers reviewed. Nineteen studies met the inclusion criteria, 18 of which were conducted in secondary care settings with one from a screening study cohort. All studies used histology obtained by transrectal ultrasound-guided biopsy (TRUS) as a reference test; usually only for patients with elevated PSA or abnormal prostate examination. Pooled data from 14,489 patients found estimated sensitivity of PSA for prostate cancer was 0.93 (95% CI 0.88, 0.96) and specificity was 0.20 (95% CI 0.12, 0.33). The area under the hierarchical summary receiver operator characteristic curve was 0.72 (95% CI 0.68, 0.76). All studies were assessed as having a high risk of bias in at least one QUADAS-2 domain.Conclusions: Currently available evidence suggests PSA is highly sensitive but poorly specific for prostate cancer detection in symptomatic patients. However, significant limitations in study design and reference test reduces the certainty of this estimate. There is very limited evidence for the performance of PSA in primary care, the healthcare setting where most PSA testing is performed.

10 August 2018 in Advances in Therapy
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SMSamuel Merriel
Samuel Merriel
GFGarth Funston
Garth Funston
WHWillie Hamilton
Willie Hamilton
Prostate cancer is a common malignancy seen worldwide. The incidence has risen in recent decades, mainly fuelled by more widespread use of prostate-specific antigen (PSA) testing, although prostate cancer mortality rates have remained relatively static over that time period. A man’s risk of prostate cancer is affected by his age and family history of the disease. Men with prostate cancer generally present symptomatically in primary care settings, although some diagnoses are made in asymptomatic men undergoing opportunistic PSA screening. Symptoms traditionally thought to correlate with prostate cancer include lower urinary tract symptoms (LUTS), such as nocturia and poor urinary stream, erectile dysfunction and visible haematuria. However, there is significant crossover in symptoms between prostate cancer and benign conditions affecting the prostate such as benign prostatic hypertrophy (BPH) and prostatitis, making it very challenging to distinguish between them on the basis of symptoms. The evidence for the performance of PSA in asymptomatic and symptomatic men for the diagnosis of prostate cancer is equivocal. PSA is subject to false positive and false negative results, affecting its clinical utility as a standalone test. Clinicians need to counsel men about the risks and benefits of PSA testing to inform their decision-making. Digital rectal examination (DRE) by primary care clinicians has some evidence to show discrimination between benign and malignant conditions affecting the prostate. Patients referred to secondary care for diagnostic testing for prostate cancer will typically undergo a transrectal or transperineal biopsy, where a number of samples are taken and sent for histological examination. These biopsies are invasive procedures with side effects and a risk of infection and sepsis, and alternative tests such as multiparametric magnetic resonance imaging (mpMRI) are currently being trialled for their accuracy and safety in diagnosing clinically significant prostate cancer.

1 March 2024 in BMC Medicine
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LDLiz Down
Liz Down
MBMelissa Barlow
Melissa Barlow
SBSarah Bailey
Sarah Bailey
LMLuke Mounce
Luke Mounce
SMSamuel Merriel
Samuel Merriel
TMTanimola Martins
Tanimola Martins
Background: Black men have higher prostate-specific antigen (PSA) levels and higher prostate cancer incidence and mortality than White men, while Asian men tend to have lower prostate cancer incidence and mortality than White men. Much of the evidence comes from the USA, and information from UK populations is limited. Methods: This retrospective cohort study used data on patients registered at general practices in England contributing to the Clinical Practice Research Datalink (CPRD) Aurum dataset. Those eligible were men aged 40 and over with a record of ethnicity and a PSA test result recorded between 2010 and 2017 with no prior cancer diagnosis. The aim was to assess the incidence of prostate cancer following a raised PSA test result in men from different ethnic groups. Additionally, incidence of advanced prostate cancer was investigated. Cancer incidence was estimated from multi-level logistic regression models adjusting for potential confounding factors. Results: 730,515 men with a PSA test were included (88.9% White). Black men and men with mixed ethnicity had higher PSA values, particularly for those aged above 60 years. In the year following a raised PSA result (using age-specific thresholds), Black men had the highest prostate cancer incidence at 24.7% (95% CI 23.3%, 26.2%); Asian men had the lowest at 13.4% (12.2%, 14.7%); incidence for White men was 19.8% (19.4%, 20.2%). The peak incidence of prostate cancer for all groups was in men aged 70–79. Incidence of prostate cancer diagnosed at an advanced stage was similar between Black and White men. Conclusions: More prostate cancer was diagnosed in Black men with a raised PSA result, but rates of advanced prostate cancer were not higher in this group. In this large primary care-based cohort, the incidence of prostate cancer in men with elevated PSA levels increases with increasing age, even when using age-adjusted thresholds, with Black men significantly more likely to be diagnosed compared to White or Asian men. The incidence of advanced stage prostate cancer at diagnosis was similar for Black and White men with a raised PSA result, but lower for Asian men.

25 June 2016 in Family Practice
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SMSamuel Merriel
Samuel Merriel
RCRobert Carroll
Robert Carroll
FHFergus Hamilton
Fergus Hamilton
WHWillie Hamilton
Willie Hamilton
The association between hypoalbuminaemia and a new diagnosis of cancer is as yet unknown. This study aimed to assess whether unexplained hypoalbuminaemia was associated with an increased risk of subsequent new cancer diagnosis within the next 12 months. A cohort study was performed using a large UK database of adult primary care patients. Patients with a serum albumin test, either low or normal, were followed for 12 months for a new diagnosis of non-skin cancer. Logistic regression was used to assess for relationships between hypoalbuminaemia and cancer diagnoses. A total of 100 122 participants had at least one albumin test result. Of these, 5753 (5.75%) had a result <35g/l, of whom 1634 developed cancer within 12 months. Of the 94 116 patients with normal albumin values, 13 906 developed cancer. Hypoalbuminaemia was associated with an increased risk of subsequent cancer diagnosis within 12 months (odds ratio [OR]: 2.29; 95% confidence interval [CI]: 2.15–2.43). This association was smaller in magnitude after controlling for other conditions known to affect albumin levels (OR: 1.29; 95% CI: 1.12–1.49). Low albumin levels were associated with an increased risk of cancer. This finding needs to be confirmed in other primary care populations.

11 February 2019 in BJU International
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SMSamuel Merriel
Samuel Merriel
LHLiz Hetherington
Liz Hetherington
ASAndrew Seggie
Andrew Seggie
JCJoanna T. Castle
Joanna T. Castle
WCWilliam Cross
William Cross
TSthe Prostate Cancer UK Expert Reference Group on Active Surveillance
the Prostate Cancer UK Expert Reference Group on Active Surveillance
Objectives: To develop a consensus statement on current best practice of active surveillance ( AS ) in the UK , informed by patients and clinical experts. Subjects and Methods: A consensus statement was drafted on the basis of three sources of data: systematic literature search of national and international guidelines; data arising from a Freedom of Information Act request to UK urology departments regarding their current practice of AS ; and survey and interview responses from men with localized prostate cancer regarding their experiences and views of AS . The Prostate Cancer UK Expert Reference Group ( ERG ) on AS was then convened to discuss and refine the statement. Results: Guidelines and protocols for AS varied significantly in terms of risk stratification, criteria for offering AS , and protocols for AS between and within countries. Patients and healthcare professionals identified clinical, emotional and process needs for AS to be effective. Men with prostate cancer wanted more information and psychological support at the time of discussing AS with the treating team and in the first 2 years of AS , and a named healthcare professional to discuss any questions or concerns they had. The ERG agreed 30 consensus statements regarding best practice for AS . Statements were grouped under headings: ‘Inclusion/Exclusion Criteria’; ‘AS follow‐up protocol’ and ‘When to stop AS’. Conclusion: Significant variation currently exists in the practice of AS in the UK and internationally. Men have clear views on the level of involvement in treatment decisions and support from their treating professionals when receiving AS . The Prostate Cancer UK AS ERG has developed a set of consensus statements for best practice in AS . Evidence for best practice in AS , and the use of multiparametric magnetic resonance imaging in AS , is still evolving, and further studies are needed to determine how to optimize AS outcomes.

19 November 2020 in BMJ Open
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Journal Article
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TMTanimola Martins
Tanimola Martins
SMSamuel Merriel
Samuel Merriel
WHWillie Hamilton
Willie Hamilton
Background Most cancers in sub-Saharan Africa (SSA) are diagnosed at advanced stages, with limited treatment options and poor outcomes. Part of this may be linked to various events occurring in patients’ journey to diagnosis. Using the model of pathways to treatment, we examined the evidence regarding the routes to cancer diagnosis in SSA. Design and settings A systematic review of available literature was performed. Methods The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. Between 30 September and 30 November 2019, seven electronic databases were searched using terms relating to SSA countries, cancer and routes to diagnosis comprising the population, exposure and outcomes, respectively. Citation lists of included studies were manually searched to identify relevant studies. Furthermore, ProQuest Dissertations & Theses Global was searched to identify appropriate grey literature on the subject. Results 18 of 5083 references identified met the inclusion criteria: eight focused on breast cancer; three focused on cervical cancer; two each focused on lymphoma, Kaposi’s sarcoma and childhood cancers; and one focused on colorectal cancer. With the exception of Kaposi’s sarcoma, definitive diagnoses were made in tertiary healthcare centres, including teaching and regional hospitals. The majority of participants initially consulted within primary care, although a considerable proportion first used complementary medicine before seeking conventional medical help. The quality of included studies was a major concern, but their findings provided important insight into the pathways to cancer diagnosis in the region. Conclusion The proportion of patients who initially use complementary medicine in their cancer journey may explain a fraction of advanced-stage diagnosis and poor survival of cancer in SSA. However, further research would be necessary to fully understand the exact role (or activities) of primary care and alternative care providers in patient cancer journeys.