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Fulltext An integrated approach for platoon-based simulation and its feasibility assessment

Ng KM, Reaz MB

PLoS One, 2015;10(3):e0114406.
PMID: 25785693 DOI: 10.1371/journal.pone.0114406

Research on developing mathematical and simulative models to evaluate performance of signalized arterials is still ongoing. In this paper, an integrated model (IM) based on Rakha vehicle dynamics and LWR model is proposed. The IM which imitates actuated performance measurement in signalized arterials is described using continuous timed Petri net with variable speeds (VCPN). This enables systematic discretized description of platoon movement from an upstream signalized intersection towards a downstream signalized intersection. The integration is based on the notion that speed and travel time characteristics in a link can be provided using Rakha model. This will assist the LWR to estimate arrival profiles of vehicles at downstream intersection. One immediate benefit of the model is that platoon arrival profile obtained from the IM can be directly manipulated to estimate queues and delays at the target intersection using input-output analysis without considering the effect of shockwaves. This is less tedious as compared to analysing the LWR model through tracing trajectory of shockwave. Besides, time parameters of a platoon could be estimated for self-scheduling control approach from a cycle to cycle basis. The proposed IM is applied to a test intersection where simulated queues and average delays from the IM are compared with the platoon dispersion model (PDM) implemented in TRANSYT, cell transmission model (CTM) and HCM2000 for both under-saturated and oversaturated situations. The comparisons yielded acceptable and reasonable results, thus ascertained the feasibility and validity of the model.
Fulltext Platoon Interactions and Real-World Traffic Simulation and Validation Based on the LWR-IM

Ng KM, Reaz MB

PLoS One, 2016;11(1):e0144798.
PMID: 26731745 DOI: 10.1371/journal.pone.0144798

Platoon based traffic flow models form the underlying theoretical framework in traffic simulation tools. They are essentially important in facilitating efficient performance calculation and evaluation in urban traffic networks. For this purpose, a new platoon-based macroscopic model called the LWR-IM has been developed in [1]. Preliminary analytical validation conducted previously has proven the feasibility of the model. In this paper, the LWR-IM is further enhanced with algorithms that describe platoon interactions in urban arterials. The LWR-IM and the proposed platoon interaction algorithms are implemented in the real-world class I and class II urban arterials. Another purpose of the work is to perform quantitative validation to investigate the validity and ability of the LWR-IM and its underlying algorithms to describe platoon interactions and simulate performance indices that closely resemble the real traffic situations. The quantitative validation of the LWR-IM is achieved by performing a two-sampled t-test on queues simulated by the LWR-IM and real queues observed at these real-world locations. The results reveal insignificant differences of simulated queues with real queues where the p-values produced concluded that the null hypothesis cannot be rejected. Thus, the quantitative validation further proved the validity of the LWR-IM and the embedded platoon interactions algorithm for the intended purpose.
Fulltext Pharmacist-structured review of proton pump inhibitor utilisation in primary care: A nonrandomised control study

Wong SL, Sulaiman N, Ng KM, Lee ZY

Malays Fam Physician, 2021 Nov 30;16(3):87-96.
PMID: 34938396 DOI: 10.51866/oa1153

Introduction: In the primary care setting, proton pump inhibitor (PPI) overutilisation often stems from the failure to discontinue prophylaxis treatment prior to tertiary care discharge and consider step-down therapy following discharge. Long-term PPI use can result in potential drug-related problems and unnecessary drug expenditure. This study aimed to evaluate the effectiveness of pharmacist-structured review in reducing inappropriate PPI prescriptions and estimate the potential cost saving.
Methods: This non-randomised controlled study was conducted for 16 weeks at 17 government health clinics in Selangor, Malaysia. Eligible patients attending the outpatient pharmacies of intervention clinics were recruited consecutively and their consent was obtained. A structured review of PPIs was performed in which pharmacists identified patient demographics, indications and the length of PPI therapy using a PPI intervention form. Recommendations were discussed with physicians before prescription changes were made and documented. Moreover, standard management was conducted in the control clinics.
Results: A total of 568 patients with prescriptions containing PPIs were sampled, with a total of 284 patients being placed into the control and intervention groups, respectively. Compared to the control group, inappropriate PPI utilisation in the intervention group significantly decreased from 79.9 to 30.4% (p<0.05). The changes to PPI prescriptions observed in the intervention group included: stop PPI therapy (30.8%), step-down therapy (22.9%), start substitution therapy (15.9%) and no change (30.4%). The physicians' acceptance rate for pharmacist intervention was 67.8%. A 66.1% reduction in monthly PPI pill count and a 72.0% reduction in monthly medication expenditure (RM44.85/patient/year) were observed.
Conclusion: The pharmacist-structured review was effective in increasing appropriate PPI utilisation and led to substantial cost savings.
Stopping anti-tumour necrosis factor therapy in patients with perianal Crohn's disease

Mak JWY, Tang W, Yip TCF, Ran ZH, Wei SC, Ahuja V, et al.

Aliment Pharmacol Ther, 2019 12;50(11-12):1195-1203.
PMID: 31638274 DOI: 10.1111/apt.15547

BACKGROUND: Little is known of the outcome of patients with perianal Crohn's disease after stopping anti-tumour necrosis factor (TNF) therapy.
AIM: To evaluate the rate of relapse in perianal Crohn's disease (CD) after stopping anti-TNF therapy.
METHODS: Consecutive perianal CD patients treated with anti-TNF therapy with subsequent discontinuation were retrieved from prospective inflammatory bowel disease database of institutes in Hong Kong, Shanghai, Taiwan, Malaysia, Thailand and Singapore from 1997 to June 2019. Cumulative probability of perianal CD relapse was estimated using Kaplan-Meier method.
RESULTS: After a median follow-up of 89 months (interquartile range [IQR]: 65-173 months), 44 of the 78 perianal CD patients (56.4%) relapsed after stopping anti-TNF, defined as increased fistula drainage or recurrence of previously healed fistula, after stopping anti-TNF therapy. Cumulative probabilities of perianal CD relapse were 50.8%, 72.6% and 78.0% at 12, 36 and 60 months, respectively. Younger age at diagnosis of CD [adjusted hazard ratio (HR): 1.04; 95% CI 1.01-1.09; P = .04] was associated with a higher chance of perianal CD relapse. Among those with perianal CD relapse (n = 44), retreatment with anti-TNF induced remission in 24 of 29 patients (82.8%). Twelve (27.3%) patients required defunctioning surgery and one (2.3%) required proctectomy. Maintenance with thiopurine was not associated with a reduced likelihood of relapse [HR = 1.10; 95% CI: 0.58-2.12; P = .77]. Among the 17 patients who achieved radiological remission of perianal CD, five (35.3%) developed relapse after stopping anti-TNF therapy after a median of 6 months.
CONCLUSIONS: More than half of the perianal CD patients developed relapse after stopping anti-TNF therapy. Most regained response after resuming anti-TNF. However, more than one-fourth of the perianal CD patients with relapse required defunctioning surgery. Radiological assessment before stopping anti-TNF is crucial in perianal CD.