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Tomoaki Imamura

Publications and source records attributed to Tomoaki Imamura.

At least 19 recordsLinked to original sources
PubMed2006

A technique for identifying three diagnostic findings using association analysis.

In diagnosing diseases in clinical practice, a combination of three clinical findings is often used to represent each disease. This is largely because it is often difficult or impractical to assess for all possible combinations of symptoms and abnormal exam findings that occur in any particular disease. For most diseases, diagnostic triads are based on empirical observations. In this study, we determined diagnostic triads for chronic diseases using data mining procedures. We also verified the combinations' validity as well as our procedure for determining them. We used symptoms and examination findings from 477 patients with chronic diseases, collected as part of a 35-year longitudinal study begun in 1968. For each patient there were 295 items from examinations in internal medicine, dermatology, ophthalmology, dentistry and blood tests. We judged each item to be either normal or abnormal, and restricted the analysis to the abnormal findings. To analyze such an exhaustive assortment, we used the data mining technique of association analysis. The analysis generated three clinical findings for each disease. Diseases were defined based on blood tests. Searching through all 295 items to find the three most useful clinical findings would be impractical on a commodity PC. However, by excluding normal items, we were able to sufficiently reduce the total number of combinations so as to make combinatorial analysis on a PC feasible. In addition to more accurate diagnoses, we believe our technique can identify those diagnostic data that are more cost effective in terms of time and other resources required for their collection.

Data Collection↗
PubMed2006

Price differences between Japan and the US for medical materials and how to reduce them.

INTRODUCTION: Previous reports (1996, 1997) have revealed that the market prices of medical materials in Japan were two to four times higher than those in the US. The Japanese government introduced the foreign price adjustment rule (FPA) in 2002 to reduce reimbursement prices in Japan. We aimed to investigate the current price differences between Japan and the US in the first half of 2005 and to evaluate the effectiveness of the FPA. METHODS: The investigation was performed at two joint purchasing organizations (JPO) and a hospital group in the US, and at a university hospital in Japan. Forty-one items in 14 categories were selected in advance. RESULTS: The price ratio (Japanese price/US price) was largest at 4.5-6.8 for percutaneous transluminal coronary angioplasty (PTCA) balloon catheters and 1.4-6.0 for vascular grafts. The price ratio was smallest at 1.2-2.4 for automatic sutures, 1.4-1.6 for Swan-Ganz catheters, and 1.5-2.3 for mechanical valves. DISCUSSION: The price differences between Japan and the United States were found to have rather widened with the exception of the pacemaker, because their market prices decreased more markedly in the United States. The investigation suggests several problems with the FPA: (1) the determination process of reimbursement prices is inappropriate, which has made the Japanese market less competitive, (2) the FPA needs too much time for the resolution of price differences, and (3) price data collected according to the FPA lacks strictness. CONCLUSIONS: The high prices of medical material in Japan need to be adjusted down with more appropriate measures such as the full cost or cost inclusion methods.

Commerce↗
PubMed2006

Women's anxieties caused by false positives in mammography screening: a contingent valuation survey.

BACKGROUND: Breast cancer screening with mammography has been shown to be effective for preventing breast cancer death. However, mammography screening can be harmful to women. One of the major problems is anxiety from a false positive result. Previous studies do not consider intangible benefits related to anxiety or peace of mind in mammography screening. In order to quantify anxiety, we employed the contingent valuation method (CVM) to measure the general public's willingness to pay (WTP) for mammography screening. METHODS: About 397 women aged 50-59 participated in the computer-assisted questionnaire survey. For the WTP question format, the double-bound dichotomous choice approach was employed. Participants were randomly assigned into 2 groups. Group A (n = 200) was provided with information about the procedure, detection rate and mortality reduction of mammography screening. Group B (n = 197) was provided with additional information including possibility of false positives and the risks of close examinations. RESULTS: The mean WTP was significantly greater in Group A than in Group B ($16.82 vs. $12.89, P = 0.02). A Weibull regression analysis showed that, type of information, history of receiving mammography screening, family history of cancer, and the degree of concern about health were significant factors affecting WTP. CONCLUSIONS: Women must be well informed before making decisions about mammography screening. Although anxiety from information about false positives significantly decreased the women's benefit, the amount of WTP in the well-informed group was still considerable. The results suggest that women can balance the anxiety against the effectiveness.

Anxiety↗
PubMed2006

Willingness to pay for health care services in common cold, retinal detachment, and myocardiac infarction: an internet survey in Japan.

BACKGROUND: The application of Willingness To Pay (WTP) measurement with Contingent Valuation Method (CVM) to medical services is gradually increasing. Knowing what influences WTP is an important matter because validity of CVM in medical services remains controversial. The objective of this survey is to measure WTP for the treatment of typical acute illnesses and to analyze the factors affecting WTP. METHODS: A questionnaire survey was conducted over the Internet, in which 795 men and women between 40 and 59 years old responded to questions about WTP for medical expenses in three hypothetical scenarios: common cold (CC), retinal detachment (RD) and myocardiac infarction (MI). RESULTS: Mean WTP was $29.9 for CC, $2,233 for RD, and $8,976 for MI. WTP for RD and MI was lower in the low-income group. While WTP for CC did not vary with income, WTP was higher in groups whose current subjective fitness levels were low. CONCLUSION: Although WTP measurements are criticized frequently for their validity and reliability, they are still useful for determining the economic value of medical services. Based on the results of this study, it is deemed necessary to enhance safety nets for low-income earners in regards to serious illnesses that incur high medical expenses. Further, it is recommended that the rate of co-payments be set relatively high with respect to mild illnesses for which alternative services are available.

Adult↗
PubMed2006

The measurement of willingness to pay for mass cancer screening with whole-body PET (positron emission tomography).

OBJECTIVE: Recently, we have seen an increase in the number of studies that measured the willingness to pay (WTP) for medical services using the contingent valuation method (CVM) and evaluated the benefits of these services. This study aimed to measure the general public's WTP for cancer screening with positron emission tomography (PET) and to determine consumer characteristics that may affect their WTP. METHODS: A questionnaire survey of males and females living in Japan aged between 40 and 59 years was conducted via the Internet. A total of 274 individuals accepted the offer to participate and were enrolled in the study. The study participants were divided into two groups: Group A (n = 138) and Group B (n = 136). Group A was provided only with information about the PET procedure and the high cancer detection rate; Group B was provided with additional information regarding the possibility of 'false negative' and 'false positive' results and the fact that the efficacy of PET screening for reducing mortality has not yet been demonstrated. Participants were then asked to answer their WTP for cancer screening with PET by paymentcards approach. RESULTS: The overall average amount consumers were willing to pay for PET cancer screening was dollars 103.7 (n = 274). The average value in Group A was dollars 107.3, the average value in Group B was dollars 100.0 and there was no statistically significant difference between the groups. The results of categorical regression analysis showed that household annual income was the only significant factor affecting WTP. CONCLUSIONS: Our study showed that household annual income affected the WTP for cancer screening with PET and therefore the demand for PET screening would be limited to the high-income group. Negative information about PET did not reduce the WTP. This finding suggests that test subjects mainly evaluated the high detection rate of PET screening and the 'reassurance' value of receiving negative screening results.

Adult↗
PubMed2006

Influence of Japan's new Diagnosis Procedure Combination-based payment system on the surgical sector: does it really shorten the hospital stay?

PURPOSE: In 2003, the Diagnosis Procedure Combination (DPC)-based payment system was introduced on a trial basis in 82 major Japanese hospitals. We analyzed the influence of this system on hospital revenue and expenditure, focusing on whether it reduces the length of stay in hospital (LOS), particularly in the surgical sector. METHODS: We studied 120 patients hospitalized at the University of Tokyo hospital between May and July 2003, including 93 surgical patients who underwent operations for gastric, colon, rectal, hepatic, or mammary carcinoma; arteriosclerosis obliterans; appendicitis; adult hernia inguinalis; or varicose veins, and 27 nonsurgical patients hospitalized for recurrent gastric carcinoma, ileus, appendicitis, or mild acute pancreatitis. We analyzed the changes in profit per day in patients with a reduced LOS using the simulation model. RESULTS: Reducing the LOS of the surgical patients resulted in a greater profit; however, there was minimal if any profit increase achieved by reducing the LOS of the medical patients. In fact, when material costs were high, profit decreased. CONCLUSION: The DPC-based payment system does not usually offer an economic incentive to shorten the LOS. Expanding our current system will reduce the LOS only in major hospitals, but it will reduce the national average LOS. Thus, the current DPC-based payment system needs to be improved further.

Cost-Benefit Analysis↗
PubMed2006

Benefit evaluation of mass screening for prostate cancer: willingness-to-pay measurement using contingent valuation.

OBJECTIVES: Cancer screening exists to save lives. However, the mortality-reducing effect of prostate cancer screening has not yet been sufficiently demonstrated. Therefore, screening should only be performed in men well informed about the disease. We hypothesized that having sufficient information will reduce men's desire for screening. To verify this hypothesis, we measured the willingness to pay (WTP) for prostate-specific antigen screening using the contingent valuation method. METHODS: A computer-based questionnaire was implemented through the Internet for 137 men in Japan aged 40 to 59 years. Participants were randomly assigned to two subgroups: 69 subjects were provided with information about the detection rate, and 68 were provided with additional information such as the failure to demonstrate the mortality-reducing effect of prostate-specific antigen screening to date. All were asked about their WTP by a payment cards approach. RESULTS: The mean WTP for prostate-specific antigen screening was 18.90 dollars. Categorical regression analysis suggested that annual income, age, and hospitalization history were factors affecting the WTP. Unexpectedly, the difference in the mean WTP between the ill-informed and well-informed groups was not statistically significant. CONCLUSIONS: The contingent valuation method can quantify comprehensive benefits, including not only health outcomes, but also non-health outcomes such as reassurance value. The subjects were not so concerned about the long-term effectiveness of saving lives. Their greatest concern was the detection rate. Their WTP may have reflected their desire for the reassurance that could be obtained by confirming that they had no physical sign of cancer.

Adult↗
PubMed2006

Analysis of factors affecting willingness to pay for cardiovascular disease-related medical services.

Recently, application of the contingent valuation method (CVM) to health care is increasing to measure the willingness to pay (WTP) for specific medical services. In this study, we measured WTP for the outpatient treatment of hypertension and inpatient treatment of myocardial infarction (MI) in Japan's healthcare system, using CVM via an Internet questionnaire survey in 547 citizens aged 40 to 49 years. WTP was measured with the payment cards method from an ex post consumer based perspective. The payment vehicle was out-of-pocket copayment under public medical insurance. The participants were asked their preferences with respect to medical institutions, and 3 comprehensive characteristics were extracted from the requested information by principal component analysis. Categorical regression was performed to analyze the factors affecting WTP. The mean WTP for hypertension treatment was 75.03 dollars/month, and that for the treatment of MI was 8,928.70 dollars (1 dollar = 105 Japanese yen). WTP for hypertension treatment was significantly high in married males and the group without symptoms, but was not associated with income. WTP for the treatment of MI was significantly high in the high-income group, married males, and the group with symptoms. Among the 3 principle components, "objective evaluation" was significantly associated with WTP for the treatment of MI. As for serious diseases such as MI, the income-associated differences in WTP suggest the necessity for reinforcement of the safety net for the low-income group. Although asymptomatic, hypertension requires continuous treatment. For such diseases, uniformly low copayment should be established irrespective of annual income.

Adult↗
PubMed2006

[Medical research using Internet questionnaire in Japan].

As the method for questionnaire studies, mail survey and interview survey are frequently used. The utility and validity of applying the Internet method to medical studies have yet to be fully evaluated. For the present investigation, we reviewed 36 Japanese original articles using Internet questionnaire reported through to April 2005. Although original papers using the Internet method have been increasing in recent years, they are still limited in number. There is comparatively much research on disease with many patients in youth and early manhood, such as allergic ailments (allergic rhinitis, atopic dermatitis, and hives). As compared with conventional methods, the advantages of the Internet approach are convenience for both investigators and respondents and the ability to quickly collect data. The disadvantage is that the user's age range is more concentrated. Since samples are extracted from individuals who are registered as monitors, a greater sampling error may occur as compared with a random sampling method. However, it is to be expected that continued explosive growth of the Internet would decrease the limitation in user's age. If more elderly people participate in questionnaire studies using the web, research into more illnesses should be facilitated. Considering the inherent advantage, it is thought that Internet method can become the leading tool for sociomedical and clinical research in the near future.

Adolescent↗
PubMed2006

[Contingent valuation for health care services. Review of domestic studies and outline of foreign investigations].

Contingent valuation method (CVM) can be applied to measure benefits of healthcare services. It is a technique for estimating subjects' willingness to pay (WTP) for a service under the scenario describing a virtual market with a questionnaire. In the present research, we outlined foreign studies and reviewed domestic studies on healthcare contingent valuation. A total of 14 papers from domestic literature (five English and nine Japanese articles) identified with mechanical search engines were verified for the following eight items: the method of the questionnaire; the information included in the virtual scenario; the question form for the willingness to pay; bias problems specific to CVM; validity/reliability, ex post/ex ante valuation, altruistic WTP, and non-health value. The following conclusions were drawn from the domestic studies: (1) several studies were short of sufficient information regarding the virtual scenario; (2) no research proved the existence of bias and the ways of coping with it; (3) tests for reliability were not carried out, although some kind of validity was verified; (4) all involved ex post user based evaluation; (5) neither altruistic WTP nor non-health value was examined. Taken the advantages of CVM into consideration, it should become a useful tool, complementing other economic evaluation techniques. Since its application has just begun in Japan, more emphasis needs to be given to practical issues so that healthcare workers will utilize CVM in a way that domestic studies in health economics will be activated.

Attitude to Health↗
PubMed2005

Impact of the Japanese Diagnosis Procedure Combination-based Payment System on cardiovascular medicine-related costs.

In 2003, a lump-sum payment system based on Diagnosis Procedure Combinations (DPC) was introduced to 82 specific function hospitals in Japan. While the US DRG/PPS system is a "per case payment" system, the DPC based payment system adopts a "per day payment." It is generally believed that the Japanese system provides as much of an incentive as the DRG/PPS system to shorten the average length of stay (LOS). We performed an empirical analysis of the effect of LOS shortening on hospital revenue and expenditure under the DPC-based payment system, particularly in cardiovascular diseases. We also point out fundamentally controversial aspects of the current system. A total 109 cases were selected from patients hospitalized at the University of Tokyo Hospital from May to July, 2003 and classified into one of three categories: (1) cardiac catheter interventions, (2) cardiac catheter examinations, and (3) other conservative treatments. We analyzed the changes in profit per day in cases of a reduction in average LOS and an increase in the number of cases. In category (1) profit increased significantly in conjunction with reduced LOS. In category (2) profit increased only minimally. In category (3), profit increased rarely and sometimes decreased. In cases of conservative treatment, profits sometimes decreased because an increase in material costs exceeded the increase in revenue. It therefore became clear that the DPC-based payment system does not decisively provide an economic incentive to reduce LOS in cardiovascular medicine.

Cardiac Catheterization↗
PubMed2005

[Evaluation of dermatological symptoms of Yusho patients in the annual examination in 2003-2004].

We evaluated the severity grades and the skin severity scores of the skin symptoms who visited the annual examinations of Fukuoka prefecture in 2003 and 2004. The severity of skin symptoms improved significantly in the first 20 years; nowadays, however, further improvement can hardly be observed. More than 36 years have passed since the Yusho incident, and about 60% of the patients currently present no skin symptoms. In contrast, in about 40% of the patients, characteristic skin symptoms of Yusho, such as pigmentation of skin, black comedones and acneform eruptions, could still be observed. Using Peason's correlation coefficient test and Spearman's correlation coefficient test, we analyzed correlation between "PCB pattern" and the blood PCB concentration, the skin severity grade and the skin severity scores. However, we could not find out any obvious correlation.

Biomarkers↗
PubMed2004

[Inter-laboratory evaluation studies for development of notified ELISA methods for allergic substances (milk)].

Extracts of sausage, sauce, cookie, cereal and pasta sauce spiked with milk standard protein at a level of 5-20 ng/mL as sample solutions were analyzed in replicate in 10 laboratories. Coefficients of variation (CVs) of the three ELISA methods using a Milk Protein Casein ELISA Kit (Casein kit), a Milk Protein Beta-Lactoglobulin ELISA Kit (Beta-Lactoglobulin kit) and a FASTKIT Milk ELISA Kit (Milk ELISA kit) were mostly below 10%. Mean recoveries of the milk standard protein from the food extracts were over 40% in the three ELISA methods with a few excertions. The recoveries of milk standard protein from the sauce extract in Casein kit were improved by adjusting the extract to neutrality before the Casein kit assay. The recoveries of milk standard protein from cookie, cereal and pasta sauce were improved by the increasing the amount of antibody coated in the Milk ELISA kit. The detection limits of all the ELISA methods were 1 ng/mL in sample solutions. These results suggested that the notified ELISA methods are reliable and reproducible for the inspection of milk protein levels in extracts of sausage, sauce, cookie, cereal and pasta sauce.

Allergens↗
PubMed2004

[Inter-laboratory evaluation studies for development of notified ELISA methods for allergic substances (wheat)].

Extracts of sausage, sauce, pasta sauce, fish paste and cereal spiked with wheat standard protein at a level of 5-20 ng/mL as sample solutions were analyzed in replicate in 10 laboratories. Coefficients of variation (CVs) of both ELISA methods using a Wheat Protein ELISA Kit (Gliadin kit) and a FASTKIT Wheat ELISA Kit (Wheat ELISA kit) were mostly below 10%. Mean recoveries of the wheat standard protein from the food extracts were over 40% in the two ELISA methods except those from cereal extract determined using the Wheat ELISA kit. Repeatability relative standard deviations of wheat standard protein in the five food extracts were in the ranges of 16-26.9% and 3.7-36.2% for the Gliadin kit and the Wheat ELISA kit, respectively. Reproducibility relative standard deviations of wheat standard protein in the five food extracts were 21.6-38.5%, 29.7-53.8% for the Gliadin kit and the Wheat ELISA kit, respectively. The recoveries of wheat standard protein from the cereal extract were improved by the increasing the amount of antibody coated on the plate in the Wheat ELISA kit. The detection limits of both ELISA methods were 1 ng/mL in sample solutions. These results suggested that the notified ELISA methods are reliable and reproducible for the inspection of wheat protein levels in extracts of sausage, sauce, pasta sauce, fish paste and cereal.

Allergens↗
PubMed2004

[Inter-laboratory evaluation studies for establishment of notified ELISA methods for allergic substances (buckwheat)].

Inter-laboratory evaluation studies were conducted for the ELISA methods for allergic substances (buckwheat). Extracts of snack, bun and udon spiked with buckwheat standard protein at a level of 5-20 ng/mL as sample solutions were analyzed in replicate at 10 laboratories. Coefficients of variation (CVs) of the ELISA methods using a Buckwheat Protein ELISA Kit (Buckwheat kit) and a FASTKIT Buckwheat ELISA kit (Buckwheat ELISA kit) were mostly below 10%. Mean recoveries of the buckwheat standard protein from the food extracts were over 40% in the two ELISA methods. Repeatability relative standard deviations of buckwheat standard protein in three food extracts were in the ranges of 6.8-78.5% and 5.0-33.9% for the Buckwheat kit and the Buckwheat ELISA kit, respectively. Reproducibility relative standard deviations of buckwheat standard protein in three food extracts were 11.9-69.5% and 16.5-34.1% for the Buckwheat kit and the Buckwheat ELISA kit, respectively. The detection limits of both ELISA methods were 1 ng/mL in sample solutions. These results suggest that the notified ELISA methods are reliable and reproducible for the inspection of buckwheat protein levels in extracts of snack, bun and udon.

Allergens↗
PubMed2004

[Inter-laboratory evaluation studies for establishment of notified ELISA methods for allergic substances (peanuts)].

Inter-laboratory evaluation studies were conducted for ELISA methods for allergic substances (peanuts). Extracts of biscuit, sauce, chocolate and butter spiked with peanut standard protein at a level of 5-20 ng/mL as sample solutions were analyzed in replicate in 10 laboratories. Coefficients of variation (CVs) of the ELISA methods using a Peanut Protein ELISA Kit (Peanut kit) and a FASTKIT Peanut ELISA kit (Peanut ELISA kit) were mostly below 10%. Mean recoveries of the peanut standard protein from the food extracts were over 40% in the two ELISA methods. Repeatability relative standard deviations of peanut standard protein in four food extracts were in the ranges of 15.2-49.7% and 3.0-28.3% for the Peanut kit and the Peanut ELISA kit, respectively. Reproducibility relative standard deviations of peanut standard protein in four food extracts were 23.5-44.4%, 9.6-28.4% for the Peanut kit and the Peanut ELISA kit, respectively. The detection limits of both ELISA methods were 2-2.5 ng/mL in sample solutions. These results suggested that the notified ELISA methods are reliable and reproducible for the inspection of peanut protein levels in extracts of biscuit, sauce, chocolate and butter.

Allergens↗