Zero inflated statistical count models for analysing the costs imposed by GERD and dyspepsia

Background and study aims: Recent studies have shown that the high prevalence and the various clinical presentations of gastro-oesophageal reflux disease [GERD] and dyspepsia impose an enormous economic burden on society. Economic cost data have unique characteristics: they are counts, and they have zero inflation. Therefore, these data require special models. Poisson regression [PR], negative binomial regression [NB], zero inflated Poisson [ZIP] and zero inflated negative binomial [ZINB] regression are the models used for analysing cost data in this paper

Patients and methods: In this study, a cross-sectional household survey was distributed to a random sample of individuals between May 2006 and December 2007 in the Tehran province of Iran to determine the prevalence of gastrointestinal symptoms and disorders and their related factors. The cost associated with each item was calculated. PR, NB, ZIP and ZINB models were used to analyse the data. The likelihood ratio test and the Voung test were used to conduct pairwise comparisons of the models. The log likelihood, the Akaike information criterion [AIC] and the Bayesian information criterion [BIC] were used to compare the performances of the models

Results: According to the likelihood ratio test and the Voung test and all three criteria used to compare the performance of the models, ZINB regression was identified as the best model for analysing the cost data. Sex, age, smoking status, BMI, insurance status and education were significant predictors

Conclusion: Because the NB model demonstrated a better fit than the PR and ZIP models, over-dispersion was clearly only due to unobserved heterogeneity. In contrast, according to the likelihood ratio test, the ZINB model was more appropriate than the ZIP model. The ZINB model for the cost data was more appropriate than the other models

Statistical count models for prognosis the risk factors of hepatitis C

The aim of this study was to compare alternatives methods for analysis of zero inflated count data and compare them with simple count models that are used by researchers frequently for such zero inflated data. Analysis of viral load and risk factors could predict likelihood of achieving sustain virological response [SVR]. This information is useful to protect a person from acquiring Hepatitis C virus [HCV] infection. The distribution of viral load contains a large proportion of excess zeros [HCV-RNA under 100], that can lead to over-dispersion. This data belonged to a longitudinal study conducted between 2005 and 2010. The response variable was the viral load of each HCV patient 6 months after the end of treatment. Poisson regression [PR], negative binomial regression [NB], zero inflated Poisson regression [ZIP] and zero inflated negative binomial regression [ZINB] models were carried out to the data respectively. Log likelihood, Akaike Information Criterion [AIC] and Bayesian Information Criterion [BIC] were used to compare performance of the models. According to all criterions, ZINB was the best model for analyzing this data. Age, having risk factors genotype 3 and protocol of treatment were being significant. Zero inflated negative binomial regression models fit the viral load data better than the Poisson, negative binomial and zero inflated Poisson models

Estimation of average diagnosis and treatment costs of hepatitis C

the objective of this study was to estimate the average cost of diagnosis and treatment of hepatitis C among patients based on their treatment regime, during the one course of treatment and six-month after stopping that. Hepatitis C virus [HCV] infection is a major cause of liver-related morbidity and mortality worldwide and a major public health problem. All data for this cross-sectional study were collected from medical records of 200 patients with hepatitis C, who referred to a private gastroenterology clinic between years 2005 through 2009. Information related to the 200 patients was extracted from their medical records and finally, 77 patients of them, who their treatment was not interfering with any other disease entered in this study. Therefore diagnosis and treatment costs of these patients were calculated. Attributable costs were reported as purchasing power parity dollars [PPP$]. Mean costs of diagnosis and treatment in one course of treatment and six month after that with standard interferon plus ribavirin [INF-RBV] exceeds 3,850 PPP$ and for patients who treated with peg-interferon plus ribavirin [PEG-RIBV] was 16,494 PPP$. Also in both types of treatment, medication cost was found to be a dominant cost component. Hepatitis C represents a very important and potentially costly disease to managed care organizations. Patients with this disease require expensive drug therapies and consume significant health care resources

History of upper gastrointestinal cancers in relatives: a community-based estimate

The present study aimed to evaluate the prevalence of positive family history of these cancers in a large population-based sample of Tehran province, capital of Iran. Upper gastrointestinal [UGI] cancers [gastric and esophagus cancer] constitute a major health problem worldwide. A family history of cancer can increase the risk for developing cancer and recognized as one of the most important risk factors in predicting personal cancer risk. This study designed as a cross-sectional survey in general population [2006-2007] of Tehran province. Totally 7,300 persons [age>= 20 years] sampled by random sampling on the basis of the list of postal, of whom 6,700 persons agreed to participate [response rate 92%]. Respondents were asked if any first-degree [FDR] or second-degree [SDR] relatives had gastric or esophageal cancer. Totally, 6,453 respondents [48% male] entered to the study. The mean age of responders with positive FH was significantly higher than those with negative FH [P<0.05]. In total, 341 respondents [5.3%] reporting a history of UGI cancers in their relatives, 134[2.1%] in FDRs, and 207[3.2%] in SDRs. Our findings showed that the reported prevalence of FH of UGI cancers was relatively low and varied by specific respondent characteristics such as age and sex. However, the estimates of prevalence presented here are likely to be conservative compared with actual prevalence because of self-reported data gathering

Epidemiological features of gastro-esophageal reflux disease in Iran based on general population

The aim of this study was to evaluate the epidemiology of GERD base on population study in Tehran providence. Gastro-esophageal reflux disease [GERD] is a common and chronic problem. Recent reports from developing counties indicate increment in the incidence and prevalence of the disease over the past. This study was a cross-sectional household survey conducted from May 2006 to December 2007 in Tehran province, Iran. Participants completed a valid gastro-esophageal reflux Questionnaire. The questionnaire included personal and family characteristics such as age, gender, and educational status. In addition, interviewers asked them regarding 10 GI symptoms. Altogether 18180 individuals participated in this cross-sectional study. The mean +/- SD age of participant was 38.7 +/- 17.1 and 9072 [49.9%] were women. The prevalence of GERD was 8.85 [8.43-9.26]. There was significant relationship between age, sex, marital and educational status with GERD. GERD symptoms were more common in women, older people, individuals with low education and married people. There was overlap between GERD, irritable bowel syndrome [IBS] and uninvestigated dyspepsia [UD]. According to our finding although the prevalence of GERD in our population is less than other studies, this prevalence is increasing in recent years

Economic burden of gastro-oesophageal reflux disease and dyspepsia: a community-based study

Gastro-oesophageal reflux disease [GERD] and dyspepsia are common digestive disorders that inflict serious harm, burden and economic consequences on individuals worldwide. The aim of this study was to estimate the direct and indirect economic burden of GERD and dyspepsia in the whole population of Tehran, the capital of Iran. The study was performed on a total of 18,180 adult subjects [age > 18 years] taken as a random sample in Tehran province, Iran [2006-2007]. A valid and reliable questionnaire was used to enquire about the symptoms of GERD, dyspepsia and the frequency of the utilization of health services including physician visits, hospitalisations and productivity loss due to GERD/dyspepsia symptoms in the preceding 6 months. GERD was found in 518 [41.9% males] patients and dyspepsia in 404 patients [38.9% males]. Further 1007 subjects had both GERD and dyspepsia. The total direct costs of disease per patient for GERD, dyspepsia and their overlap were PPP$97.70, PPP$108.10 and PPP$101.30, respectively [PPP, purchasing power parity dollars]. The total indirect cost of disease per patient was PPP$13.7, PPP$12.1 and PPP$32.7, for GERD, dyspepsia and their overlap, respectively. According to our results, hospitalisation and physician visits were the main cost of disease that could be minimized by revision of the insurance business in Iran

[Frequency of colorectal cancer in healthy individual's relatives: a cross-sectional population-based study]

Family history of colorectal cancer has been shown to be related to the risk of developing colorectal cancer. This risk depends on the number of affected relatives and the age at diagnosis. In this study we aimed to estimate the frequency of a positive family history of colorectal cancer in a random sample from Tehran population. This study was a community-based cross-sectional survey conducted from May 2006 to December 2007 in Tehran province, Iran. A total of 5,500 peoples [age >/= 20 years] drawn up randomly by random sampling according to postal codes and invited to participate in the study. All participants completed a detailed health data registry form on family history status of colorectal cancer. The mean age of men with a positive family history was significantly different from men with negative family history. There was no significant difference between mean age of women responders with or without positive family history. Among all participants [n=5,500], 162 responders [2.9%] had a history of colorectal cancer. Of 162, 67 responders [1.22%] had one and 4[0.07%] had two or more first-degree relative with colorectal cancer. Of 5,500 participants, 18 subjects [0.33%] reported having two or more first-degree relative with colorectal cancer or one first-degree relative with colorectal cancer diagnosed at age<50 years. Four subjects [0.07%] had three or more first-degree relative with colorectal cancer. Based on the findings, we estimate that more than 570,000 subjects in the Iran in the age group >/= 20 years have at least two to three times increased risk of developing colorectal cancer which should be identified and encourage to participate in screening and surveillance protocols of colorectal cancer

Bloating in irritable bowel syndrome

The purpose of this study was to describe the occurrence of self report bloating and related factors n patients with irritable bowel syndrome [IBS]. Bloating symptoms are common in patients with IBS and have significant impact on normal daily function. This study was a community-based cross-sectional survey that conducted using a valid questionnaire base on Rome III criteria. Univariate analysis was used for investigation about distribution of self reported bloating according to demographic and psychological factors in irritable bowel syndrome patients. Out of 18180 subjects under study, 198 cases met criteria for the diagnosis of the irritable bowel syndrome according to criteria ROME III and 61.6% reported bloating symptoms. Bloating symptoms were more prevalent among patients with intermittent symptoms and diarrhea that in patients with constipation. Catastrophic events and depression were independent risk factors for bloating. Findings of this study support the clinical impression regarding the high prevalence of bloating symptoms in patients with irritable bowel syndrome. Further studies are needed to understand the role of physiological and psychological factors and their interaction in development of bloating in irritable bowel syndrome patients

Functional bowel disorders in Iranian population using Rome III criteria

To study the prevalence and risk factors of functional bowel disorders [FBD] in Iranian community using Rome III criteria. This study was a cross-sectional household survey conducted from May 2006 to December 2007 in Tehran province, Iran, including 18, 180 participants who were selected randomly and interviewed face-to-face by a validated questionnaire based on Rome III criteria. In all, 1.1% met the Rome III criteria for irritable bowel syndrome [IBS], 2.4% for functional constipation [FC], and 10.9% of the participants had any type of FBD. Among participants with functional dyspepsia, 83.3% had FBD; the majority cases were unspecified functional bowel disorder [U-FBD]. Of the subjects fulfilling the IBS criteria, IBS with constipation [52%] was the most frequent subtype. In the multivariate analysis, women had a higher risk of any FBDs than men, except for functional diarrhea [FD]. The prevalence of FBD, FC and FD increased and IBS decreased with increasing age. Marital status was only associated with a decrease in the risk of FBD and FD, respectively. IBS subtypes compared with FC and FD. There was no significant difference between FC and IBS with constipation [IBS-C], except for self-reported constipation; while, IBS with diarrhea [IBS-D] had more symptoms than FD. This study revealed a low rate of FBDs among the urban population of Tehran province. The ROME III criteria itself, and the problems with interpretation of the data collection tool may have contributed in underestimating the prevalence of FBD. In addition the reliability of recall over 6 months in Rome III criteria is questionable for our population

Uninvestigated dyspepsia and its related factors in an Iranian community

To determine the prevalence and determinants of uninvestigated dyspepsia in the Iranian population. A cross-sectional study conducted in Tehran province from May 2006 to December 2007, included 18,180 adult persons selected randomly. The study took place at Shahid Beheshti University, MC, Tehran, Iran. A questionnaire was completed in 2 steps. In the first part, personal characteristics and 11 gastrointestinal symptoms were inserted. Those who reported at least one of these 11 symptoms were referred for the second interview, which consisted of questions on different gastrointestinal disorders based on Rome III criteria, including uninvestigated dyspepsia. The prevalence rate of uninvestigated dyspepsia was 8.5% [10.9% in women and 6.4% in men]. Among the subjects diagnosed with dyspepsia, bothersome postprandial fullness was the most common symptom [41.5%]. Uninvestigated dyspepsia was more common in low educated and widowed participants. Approximately 41.4% of patients had a history of depression, and 66.1% had self report of stress. The prevalence of functional irritable bowel syndrome in patients with uninvestigated dyspepsia was 8.3% and gastroesophageal reflux disease was 64.9%. Uninvestigated dyspepsia has a less common prevalence in the general Iranian population than developed countries. Women, older, obese, widowed, and low education subjects are more likely to suffer from dyspepsia