Displaying publications 1 - 20 of 205 in total

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  1. Fang YY, Suraiya Kassim
    Sains Malaysiana, 2013;42:673-683.
    In competing risks analysis, the primary interest of researchers is the estimation of the net survival probability (NSP) if a cause of failure could be eliminated from a population. The Kaplan-Meier product-limit estimator under the assumption that the eliminated risk is non-informative to the other remaining risks, has been widely used in the estimation of the NSP. The assumption implies that the hazard of the remaining risks before and after the elimination are equal and it could be biased. This paper addressed this possible bias by proposing a non-parametric multistate approach that accounts for an informative eliminated risk in the estimation procedure, whereby the hazard probabilities of the remaining risks before and after the elimination of a risk are not assumed to be equal. When a non-informative eliminated risk was assumed, it was shown that the proposed multistate estimator reduces to the Kaplan-Meier estimator. For illustration purposes, the proposed procedure was implemented on a published dataset and the change in hazard after elimination of a cause is investigated. Comparing the results to those obtained from using the Kaplan-Meier method, it was found that in the presence of (both constant and non-constant) informative eliminated risk, the proposed multistate approach was more sensitive and flexible.
    Matched MeSH terms: Survival Analysis
  2. Omer ME, Mustafa M, Ali N, Abd Rahman NH
    Asian Pac J Cancer Prev, 2023 Dec 01;24(12):4167-4177.
    PMID: 38156852 DOI: 10.31557/APJCP.2023.24.12.4167
    OBJECTIVE: Cure models are frequently used in survival analysis to account for a cured fraction in the data. When there is a cure rate present, researchers often prefer cure models over parametric models to analyse the survival data. These models enable the ability to define the probability distribution of survival durations for patients who are at risk. Various distributions can be considered for the survival times, such as Exponentiated Weibull Exponential (EWE), Exponential Exponential (EE), Weibull and lognormal distribution. The objective of this research is to choose the most appropriate distribution that accurately represents the survival times of patients who have not been cured. This will be accomplished by comparing various non-mixture cure models that are based on the EWE distribution with its sub-distributions, and distributions distinct from those belonging to the EWE distribution family.

    MATERIAL AND METHODS: A sample of 85 patients diagnosed with superficial bladder tumours was selected to be used in fitting the non-mixture cure model. In order to estimate the parameters of the suggested model, which takes into account the presence of a cure rate, censored data, and covariates, we utilized the maximum likelihood estimation technique using R software version 3.5.7.

    RESULT: Upon conducting a comparison of various parametric models fitted to the data, both with and without considering the cure fraction and without incorporating any predictors, the EE distribution yields the lowest AIC, BIC, and HQIC values among all the distributions considered in this study, (1191.921/1198.502, 1201.692/1203.387, 1195.851/1200.467). Furthermore, when considering a non-mixture cure model utilizing the EE distribution along with covariates, an estimated ratio was obtained between the probabilities of being cured for placebo and thiotepa groups (and its 95% confidence intervals) were 0.76130 (0.13914, 6.81863).

    CONCLUSION: The findings of this study indicate that EE distribution is the optimal selection for determining the duration of survival in individuals diagnosed with bladder cancer.

    Matched MeSH terms: Survival Analysis
  3. Kow CS, Hasan SS
    Chest, 2021 05;159(5):2108-2109.
    PMID: 33965134 DOI: 10.1016/j.chest.2020.11.073
    Matched MeSH terms: Survival Analysis
  4. Bader Ahmad Aljawadi, Mohd Rizam Abu Bakar, Noor Akma
    MyJurnal
    This study deals with the analysis of the cure rate estimation based on the Bounded Cumulative Hazard (BCH) model using interval censored data, given that the exact distribution of the data set is unknown. Thus, the non-parametric estimation methods are employed by means of the EM algorithm. The Turnbull and Kaplan Meier estimators were proposed to estimate the survival function, even though the Kaplan Meier estimator faces some restrictions in term of interval survival data. A comparison of the cure rate estimation based on the two estimators was done through a simulation study.
    Matched MeSH terms: Survival Analysis
  5. Kiani K, Arasan J, Habshah Midi
    Sains Malaysiana, 2012;41:471-480.
    There are numerous parametric models for analyzing survival data such as exponential, Weibull, log-normal and gamma. One of such models is the Gompertz model which is widely used in biology and demography. Most of these models are extended to new forms for accommodating different types of censoring mechanisms and different types of covariates. In this paper the performance of the Gompertz model with time-dependent covariate in the presence of right censored data was studied. Moreover, the performance of the model was compared at different censoring proportions (CP) and sample sizes. Also, the model was compared with fixed covariate model. In addition, the effect of fitting a fixed covariate model wrongly to a data with time-dependent covariate was studied. Finally, two confidence interval estimation techniques, Wald and jackknife, were applied to the parameters of this model and the performance of the methods was compared.
    Matched MeSH terms: Survival Analysis
  6. Omer ME, Abu Bakar M, Adam M, Mustafa M
    Asian Pac J Cancer Prev, 2021 Apr 01;22(4):1045-1053.
    PMID: 33906295 DOI: 10.31557/APJCP.2021.22.4.1045
    OBJECTIVE: Cure rate models are survival models, commonly applied to model survival data with a cured fraction. In the existence of a cure rate, if the distribution of survival times for susceptible patients is specified, researchers usually prefer cure models to parametric models. Different distributions can be assumed for the survival times, for instance, generalized modified Weibull (GMW), exponentiated Weibull (EW), and log-beta Weibull. The purpose of this study is to select the best distribution for uncured patients' survival times by comparing the mixture cure models based on the GMW distribution and its particular cases.

    MATERIALS AND METHODS: A data set of 91 patients with high-risk acute lymphoblastic leukemia (ALL) followed for five years from 1982 to 1987 was chosen for fitting the mixture cure model. We used the maximum likelihood estimation technique via R software 3.6.2 to obtain the estimates for parameters of the proposed model in the existence of cure rate, censored data, and covariates. For the best model choice, the Akaike information criterion (AIC) was implemented.

    RESULTS: After comparing different parametric models fitted to the data, including or excluding cure fraction, without covariates, the smallest AIC values were obtained by the EW and the GMW distributions, (953.31/969.35) and (955.84/975.99), respectively. Besides, assuming a mixture cure model based on GMW with covariates, an estimated ratio between cure fractions for allogeneic and autologous bone marrow transplant groups (and its 95% confidence intervals) were 1.42972 (95% CI: 1.18614 - 1.72955).

    CONCLUSION: The results of this study reveal that the EW and the GMW distributions are the best choices for the survival times of Leukemia patients.
    .

    Matched MeSH terms: Survival Analysis*
  7. Phang KC, Hussin NH, Abdul Rahman F, Tizen NMS, Mansoor A, Masir N
    Malays J Pathol, 2019 Aug;41(2):101-124.
    PMID: 31427546
    INTRODUCTION: Diffuse large B-cell lymphoma (DLBCL) is the most common aggressive type of non-Hodgkin lymphoma with variable clinical outcomes. The immunogenotypic features of this heterogeneous disease in Malaysia were not well characterized.

    MATERIALS & METHODS: In total 141 local series of DLBCL cases from UKM Medical Centre were retrospectively studied.

    RESULTS: Of these cases, we classified our patients into two subtypes: 32.7% (37/113) GCB and non-GCB 67.3% (76/113) by Hans algorithm and the results showed strong agreement with the results by Choi algorithm (κ = 0.828, P<0.001). Survival analysis indicated significant difference in between GCB and non-GCB subtypes (P=0.01), elevated serum LDH (P=0.016), age more than 60-year-old (P=0.021) and the presence of B symptoms (P=0.04). We observed 12% DLBCL cases were CD5 positive and 81.8% of them died of the disease (P=0.076). Analysis on the dual expression of MYC/BCL2 revealed that there is no significant difference in DE and non-DE groups (P=0.916). FISH study reported there were 9.22% (13/141) rearranged cases observed in our population at which highest frequency of BCL6 gene rearrangement (76.9%), followed by MYC (15.4%) and BCL2 (7.7%); no BCL10 and MALT-1 gene rearrangement found regardless of using TMAs or whole tissue samples. More cases of MYC protein overexpression observed compared to MYC translocation.

    CONCLUSION: Relatively lower frequency of GCB tumours and low gene rearrangement rates were observed in Malaysian population. A national study is therefore warranted to know better the immunogenotypic characteristics of DLBCL in Malaysia and their implications on the survival.

    Matched MeSH terms: Survival Analysis
  8. Tan CL, Hairi NN, Awang H
    Asia Pac J Public Health, 2023 Jul;35(5):366-372.
    PMID: 37231655 DOI: 10.1177/10105395231176613
    Active aging is important for promoting the health, wellbeing, and participation of older adults. This study investigated the association between active aging and mortality risk among 2 230 respondents aged 60 and older. Principal component analysis extracted a five-factor structure from 15 indicators of active aging. The mean active aging score was 55.57 and the median was 53.33. The Kaplan-Meier curve showed that individuals with active aging scores of 53.33 and above had significantly longer survival than those below the median. Cox regression analysis indicated the significance of active aging in reducing mortality risk by 2.5% after adjusting for sex, marital status, age, ethnicity, chronic diseases, and risk factors. The active aging approach comprising health, economic, and social factors is crucial in improving survival among older adults. Hence, policies and programs that promote active aging should be encouraged to enhance the health and wellbeing of older adults and their engagement in society.
    Matched MeSH terms: Survival Analysis
  9. Go KW, Teo SM
    Transplant Proc, 2004 Sep;36(7):2046-7.
    PMID: 15518740
    To compare patient graft survival between various subgroups among renal transplant patients.
    Matched MeSH terms: Survival Analysis*
  10. Guure CB, Ibrahim NA, Adam MB
    Comput Math Methods Med, 2013;2013:849520.
    PMID: 23476718 DOI: 10.1155/2013/849520
    Interval-censored data consist of adjacent inspection times that surround an unknown failure time. We have in this paper reviewed the classical approach which is maximum likelihood in estimating the Weibull parameters with interval-censored data. We have also considered the Bayesian approach in estimating the Weibull parameters with interval-censored data under three loss functions. This study became necessary because of the limited discussion in the literature, if at all, with regard to estimating the Weibull parameters with interval-censored data using Bayesian. A simulation study is carried out to compare the performances of the methods. A real data application is also illustrated. It has been observed from the study that the Bayesian estimator is preferred to the classical maximum likelihood estimator for both the scale and shape parameters.
    Matched MeSH terms: Survival Analysis*
  11. Noor HZ, Noor HZ, Makhmudi A, Gunadi
    Med J Malaysia, 2020 05;75(Suppl 1):1-4.
    PMID: 32483103
    BACKGROUND: Many prognostic factors have been reported for the outcomes of biliary atresia (BA) patients after Kasai procedure, however, it still shows a conflicting result. Our study was to determine the impact of total bilirubin postoperative day-7 and pre-operative ratio (TB7/TB0), gammaglutamyl transferase post-operative day-7 and pre-operative ratio (GGT7/GGT0), and alanine transaminase post-operative day-7 and pre-operative ratio (ALT7/ALT0) on the survival of BA patients following Kasai surgery.

    METHODS: We reviewed the medical records of BA patients who underwent Kasai procedure at the Dr. Sardjito Hospital, Indonesia from August 2012 to December 2018. The cut-off values of TB7/TB0, GGT7/GGT0, and ALT7/ALT0 for prediction of patients' survival were determined by receiver operating characteristics (ROC) curves. Log-rank tests were utilised to test the association between cut-off values and overall survival.

    RESULTS: In all 46 BA patients (23 males and 23 females) after Kasai procedure were included, consisting of one type 1, 17 type 2A, seven type 2B, and 21 type 3. The cut-off values of TB7/TB0, ALT7/ALT0 and GGT7/GGT0 for overall survival was 0.455 (sensitivity 87.5%, specificity 22.7%, area under curve (AUC) 0.59; 95% Confidence Interval (95%CI): 0.42, 0.75), 0.481 (sensitivity 87.5%, specificity 18.2%, AUC 0.49; 95%CI: 0.31, 0.65), and and 0.31 (sensitivity 79.2%, specificity 9.1%, AUC 0.34; 95%CI: 0.18, 0.50), respectively. However, these cut-off values were not significantly associated with overall survival, with p-values of 0.18, 0.49, and 0.56, respectively.

    CONCLUSION: The TB7/TB0, ALT7/ALT0, and GGT7/GGT0 might not predict the overall survival of BA patients after Kasai procedure. Further multicentre studies with a larger sample size is needed to clarify our findings.

    Matched MeSH terms: Survival Analysis*
  12. Kong YC, Bhoo-Pathy N, Subramaniam S, Bhoo-Pathy N, Taib NA, Jamaris S, et al.
    PMID: 28420149 DOI: 10.3390/ijerph14040427
    Background: Survival disparities in cancer are known to occur between public and private hospitals. We compared breast cancer presentation, treatment and survival between a public academic hospital and a private hospital in a middle-income country. Methods: The demographics, clinical characteristics, treatment and overall survival (OS) of 2767 patients with invasive breast carcinoma diagnosed between 2001 and 2011 in the public hospital were compared with 1199 patients from the private hospital. Results: Compared to patients in the private hospital, patients from the public hospital were older at presentation, and had more advanced cancer stages. They were also more likely to receive mastectomy and chemotherapy but less radiotherapy. The five-year OS in public patients was significantly lower than in private patients (71.6% vs. 86.8%). This difference was largely attributed to discrepancies in stage at diagnosis and, although to a much smaller extent, to demographic differences and treatment disparities. Even following adjustment for these factors, patients in the public hospital remained at increased risk of mortality compared to their counterparts in the private hospital (Hazard Ratio: 1.59; 95% Confidence Interval: 1.36-1.85). Conclusion: Late stage at diagnosis appears to be a major contributing factor explaining the breast cancer survival disparity between public and private patients in this middle-income setting.
    Matched MeSH terms: Survival Analysis*
  13. Dieng H, Rajasaygar S, Ahmad AH, Ahmad H, Rawi CS, Zuharah WF, et al.
    Acta Trop, 2013 Dec;128(3):584-90.
    PMID: 23999373 DOI: 10.1016/j.actatropica.2013.08.013
    Annually, 4.5 trillion cigarette butts (CBs) are flicked into our environment. Evidence exists that CB waste is deadly to aquatic life, but their lethality to the aquatic life of the main dengue vector is unknown. CBs are full of toxicants that occur naturally, during planting and manufacturing, which may act as larvicidal agents. We assessed Aedes aegypti vulnerability to Marlboro butts during its development. Overall, CBs showed insecticidal activities against larvae. At early phases of development, mortality rates were much higher in two CBs solution (2CBSol) and 3CBSol microcosms (MICRs). Larval survival gradually decreased with development in 1CBSol-MICRs. However, in great presence of CBs, mortality was high even for the late developmental stages. These results suggest that A. aegypti larvae are vulnerable to CB presence in their habitats, but this effect was seen most during the early developmental phases and in the presence of increased amounts of cigarette remnants. CB filters are being used as raw material in many sectors, i.e., brick, art, fashion, plastic industries, as a practical solution to the pollution problem, the observed butt waste toxicity to mosquito larvae open new avenues for the identification of novel insecticide products.
    Matched MeSH terms: Survival Analysis
  14. Ebau W, Rawi CS, Din Z, Al-Shami SA
    Asian Pac J Trop Biomed, 2012 Aug;2(8):631-4.
    PMID: 23569984 DOI: 10.1016/S2221-1691(12)60110-5
    To investigate the acute toxicity of cadmium and lead on larvae of two tropical Chironomid species, Chironomus kiiensis (C. kiiensis) Tokunaga and Chironomus javanus (C. javanus) Kieffer.
    Matched MeSH terms: Survival Analysis
  15. Kuze N, Sipangkui S, Malim TP, Bernard H, Ambu LN, Kohshima S
    Primates, 2008 Apr;49(2):126-34.
    PMID: 18297473 DOI: 10.1007/s10329-008-0080-7
    We analysed the reproductive parameters of free-ranging female orangutans at Sepilok Orangutan Rehabilitation Centre (SORC) on Borneo Island, Sabah, Malaysia. Fourteen adult females produced 28 offspring in total between 1967 and 2004. The average censored interbirth interval (IBI) (i.e. offspring was still alive when mother produced a next offspring) was 6 years. This was shorter than censored IBIs reported in the wild but similar to IBIs reported for those in captivity. The nonparametric survival analysis (Kaplan-Meier method) revealed a significantly shorter IBI at SORC compared with wild orangutans in Tanjung Putting. The infant (0-3 years) mortality rate at SORC of 57% was much higher than rates reported both in the wild and captivity. The birth sex-ratio was significantly biassed toward females: 24 of the 27 sex-identified infants were females. The average age at first reproduction was 11.6 years, which is younger than the age in the wild and in captivity. The high infant mortality rate might be caused by human rearing and increased transmission of disease due to frequent proximal encounters with conspecifics around the feeding platforms (FPs). This young age of first reproduction could be because of the uncertainty regarding estimated ages of the female orangutans at SORC. It may also be affected by association with other conspecifics around FPs, which increased the number of encounters of the females with males compared with the number of encounters that would take place in the wild. Provision of FPs, which improves the nutritional condition of the females, caused the shorter IBI. The female-biassed birth sex-ratio can be explained by the Trivers and Willard hypothesis. The female-biassed sex ratio could be caused by the mothers being in poor health, parasite prevalence and/or high social stress (but not food scarcity) due to the frequent encounters with conspecifics around FPs.
    Matched MeSH terms: Survival Analysis
  16. Mohd Suan MA, Tan WL, Soelar SA, Ismail I, Abu Hassan MR
    Epidemiol Health, 2015;37:e2015017.
    PMID: 25868638 DOI: 10.4178/epih/e2015017
    OBJECTIVES: The goal of this study was to assess the relationship between intestinal obstruction and the prognosis of colorectal carcinoma.

    METHODS: Data pertaining to 4,501 colorectal carcinoma patients were extracted from the national colorectal registry and analysed. Survival analysis was performed using the Kaplan-Meier method. The log-rank test was used to compare the survival rate between patients with intestinal obstruction and those without intestinal obstruction. The p-values<0.05 were considered to indicate statistical significance. Simple Cox proportional hazards regression analysis was used to estimate the crude hazard ratio of mortality from colorectal cancer.

    RESULTS: Intestinal obstruction was reported in more than 13% of patients. The 3-year survival rate after treatment was 48.3% (95% confidence interval [CI], 43.9 to 52.8) for patients with intestinal obstruction (n=593) and 54.9% (95% CI, 53.1 to 56.6) for patients without intestinal obstruction (n=3,908). The 5-year survival rate for patients with intestinal obstruction was 37.3% (95% CI, 31.9 to 42.8), which was lower than that of patients without intestinal obstruction (45.6%; 95% CI, 43.5 to 47.7). After adjusting the hazard ratio for other prognostic variables, intestinal obstruction had a statistically significant negative correlation with the survival rate of colorectal cancer patients, with an adjusted hazard ratio of 1.22 (p=0.008).

    CONCLUSIONS: The presence of intestinal obstruction is associated with a lower survival rate among colorectal cancer patients.

    Matched MeSH terms: Survival Analysis
  17. Mohammed R, Goh KL, Wong NW
    Med J Malaysia, 1996 Mar;51(1):99-102.
    PMID: 10967987
    Primary biliary cirrhosis is an uncommon disease amongst Malaysians. Over a 12-year period, between 1979 and 1991, only seven patients with clinical, biochemical and histologic evidence of primary biliary cirrhosis were identified in University Hospital Kuala Lumpur. All were Chinese females between the ages of 30 to 55 years. The presenting complaint was pruritus in 5 patients. All except one patient was jaundiced when the diagnosis was made. These patients were followed up from 1 to 11 years. Three deaths were reported, one from massive hemetemesis and two from liver failure.
    Matched MeSH terms: Survival Analysis
  18. Ciminelli G, Garcia-Mandicó S
    J Public Health (Oxf), 2020 11 23;42(4):723-730.
    PMID: 32935849 DOI: 10.1093/pubmed/fdaa165
    BACKGROUND: There are still many unknowns about COVID-19. We do not know its exact mortality rate nor the speed through which it spreads across communities. This lack of evidence complicates the design of appropriate response policies.

    METHODS: We source daily death registry data for 4100 municipalities in Italy's north and match them to Census data. We augment the dataset with municipality-level data on a host of co-factors of COVID-19 mortality, which we exploit in a differences-in-differences regression model to analyze COVID-19-induced mortality.

    RESULTS: We find that COVID-19 killed more than 0.15% of the local population during the first wave of the epidemic. We also show that official statistics vastly underreport this death toll, by about 60%. Next, we uncover the dramatic effects of the epidemic on nursing home residents in the outbreak epicenter: in municipalities with a high share of the elderly living in nursing homes, COVID-19 mortality was about twice as high as in those with no nursing home intown.

    CONCLUSIONS: A pro-active approach in managing the epidemic is key to reduce COVID-19 mortality. Authorities should ramp-up testing capacity and increase contact-tracing abilities. Adequate protective equipment should be provided to nursing home residents and staff.

    Matched MeSH terms: Survival Analysis
  19. Qudsiah Suliman, Salmiah Md. Said, Nor Afiah Mohd. Zulkefli, Lim Poh Ying, Tan Kit-Aun
    MyJurnal
    Introduction: Despite advancement of treatment modalities, Tuberculosis (TB) treatment interruption rate has glob- ally accelerating, calling for greater framework shifting towards psychosocial intervention. Similarly, Selangor state had reported the perturbing TB treatment interruption rate, which was figured persistently above 10% in the interval year of 2014 to 2018, thus signifies an empirical assessment on Information-Motivation-Behavioural skills (IMB) determinants of TB intensive phase treatment. This study aims to determine the time to intensive phase TB treatment interruption and its prognostic factors among newly diagnosed pulmonary Tuberculosis (PTB) smear positive patients in urban district Selangor. Methods: A multi-centric prospective cohort study will recruit 695 newly diagnosed PTB smear positive patients at treatment centres in urban districts, Selangor. This study will utilize validated self-admin- istered questionnaire and standardised data collection form (PROFORMA). At baseline, we will elicit information on IMB models constructs, additionally on socio-demographics, health service factors and clinical characteristics. Meanwhile, four points follow up will be executed to retrieve information on treatment status and time varying effects of body weight, treatment side effects, symptoms improvement and internalised stigma. Finally, survival analysis will be computed to identify the time to intensive phase treatment interruption and its prognostic factors. Conclusion: This study will enlighten IMB model determinants of intensive phase treatment interruption, hence to endeavour psychosocial elements in designing time relevant public health strategies in TB case management.
    Matched MeSH terms: Survival Analysis
  20. Lau MY, Teng FE, Chua KH, Ponnampalavanar S, Chong CW, Abdul Jabar K, et al.
    Pathogens, 2021 Mar 02;10(3).
    PMID: 33801250 DOI: 10.3390/pathogens10030279
    The emergence of carbapenem-resistant Klebsiella pneumoniae (CRKP) is a great concern, as carbapenems are the last-line therapy for multidrug-resistant Gram-negative bacteria infections. This study aims to report the epidemiology of CRKP in a teaching hospital in Malaysia based on the molecular genotypic and clinical characteristics of the isolates. Sixty-three CRKP strains were isolated from a tertiary teaching hospital from January 2016 until August 2017. Carbapenemase genes were detected in 55 isolates, with blaOXA-48 (63.5%) as the predominant carbapenemase gene, followed by blaNDM (36.5%). At least one porin loss was detected in nine isolates. Overall, 63 isolates were divided into 30 clusters at similarity of 80% with PFGE analysis. Statistical analysis showed that in-hospital mortality was significantly associated with the usage of central venous catheter, infection or colonization by CRKP, particularly NDM-producers. In comparison, survival analysis using Cox proportional hazards regression identified a higher hazard ratio for patients with a stoma and patients treated with imipenem but a lower hazard ratio for patients with NDM-producing CRKP. OXA-48 carbapenemase gene was the predominant carbapenemase gene in this study. As CRKP infection could lead to a high rate of in-hospital mortality, early detection of the isolates was important to reduce their dissemination.
    Matched MeSH terms: Survival Analysis
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