Cost of illness due to Chikungunya during 2006 outbreak in a rural area in Tamil Nadu

OBJECTIVE

To estimate the burden of chikungunya in terms of financial and opportunity costs through a cross sectional survey from an affected area in Tamil Nadu.

METHODS

A survey of 809 households with a population of 4393 showed 59 individuals suffered from clinical symptoms of chikungunya. Using pre-tested questionnaire, information on the source of treatment, costs and income foregone were generated.

RESULTS

Both public and private health facilities were utilized by the patients. The per capita cost on treatment and average loss of income was Rs.223 and Rs.543 respectively. Extrapolation of this result to the entire village with 615 suspected cases showed estimates of Rs.1.38 and 3.35 lakhs towards treatment and productivity loss respectively. The cost saving per patient would be Rs. 59.93 if recommended line of treatment was followed.

CONCLUSION

The results of the study justify the need for appropriate preventive measures with active surveillance support towards epidemic preparedness.

Burden of chikungunya in India: estimates of disability adjusted life years (DALY) lost in 2006 epidemic

BACKGROUND & OBJECTIVES

During 2006, chikungunya emerged as a major ever known epidemic in India. Disability adjusted life years (DALY) is an appropriate summary measure of population health to express epidemiological burden of diseases. We estimated the burden due to suspected chikungunya using DALYs for the first time and compared between the states and also with the burden due to other vector-borne diseases in India. The economic burden was also assessed in terms of productivity loss.

METHODS

Data on the reported cases of fever/suspected cases of chikungunya from different states during 2006 in India were used. Years lived with disability (YLD) were calculated for non-fatal cases to estimate DALY. Since the disability weight for chikungunya is not available, the weights available for rheumatic arthritis, comparable to the disease outcome of chikungunya were used for the estimation. The burden was estimated for both acute and chronic cases. It is considered that about 11.5% of cases were reported to have extended morbidity with persisting arthralgia. For acute disease, the average duration of illness was considered to be nine days and for chronic cases it was six months on an average. The productivity loss due to income foregone by the working class was calculated using minimum official wage.

RESULTS

National burden of chikungunya was estimated to be 25,588 DALYs lost during 2006 epidemic, with an overall burden of 45.26 DALYs per million. It varied from 0.01 to 265.62 per million in different states. Karnataka alone contributed as high as 55% of the national burden. Persistent arthralgia was found to impose heavy burden, accounting for 69% of the total DALYs. The productivity loss in terms of income foregone was estimated to be a minimum of Rs. 391 million.

INTERPRETATION & CONCLUSION

The chikungunya epidemic in the year 2006 imposed heavy epidemiological burden and productivity loss to the community. The burden of chikungunya in terms of DALY was estimated for the first time. In view of re-emergence and spread of this infection in recent times it is warranted for derivation of disability weight for different health states of chikungunya to facilitate realistic estimates of DALYs. Quality epidemiological data from surveillance system to monitor vector-borne and zoonotic diseases would pave way for more realistic estimates of burden. The productivity loss in-terms of income foregone could be minimal as the estimation was made by using the minimum wage fixed by the government although the actual loss is expected to be higher.

A method for detecting microfilaraemia, filarial specific antigens and antibodies and typing of parasites for drug resistance and genotypes using finger prick blood sample

Monitoring and evaluation of programme to eliminate lymphatic filariasis (LF) depends on epidemiological assessment using appropriate indicators. Minimum efforts using reliable tests are necessary to guide the programme managers in decision-making. Impact of Mass Drug Administration (MDA) towards filariasis elimination can be assessed by the detection of microfilariae (mf) or parasite DNA (infective), filarial antigens (infected) and antibodies (exposure). It is also important to monitor drug resistance and variation in genetic structure of parasite populations using molecular markers. We developed a method to carry out parasitological, molecular, immunological and genetic analysis from a minimum volume of blood sample (about 150 microl) drawn from finger tip of an individual residing in LF endemic area. The method involves separation of sera for immunological assays and isolation of mf of Wuchereria bancrofti from the blood clots for counting, which were then used for W. bancrofti specific PCR, screening for albendazole sensitivity/resistance alleles by AS-PCR, RAPD profiling and ITS 2 PCR for genotyping. A protocol is also suggested for the separation of sera for assays to detect antigen and antibodies and isolation of mf from clots for genetic analysis. The protocol developed has shown potential application in monitoring several immunological, parasitological and molecular parameters from a limited amount of blood sample collected by finger prick, in large-scale operations.

Sample Size Calculation for Estimating or Testing a Nonzero Squared Multiple Correlation Coefficient

The problems of hypothesis testing and interval estimation of the squared multiple correlation coefficient of a multivariate normal distribution are considered. It is shown that available one-sided tests are uniformly most powerful, and the one-sided confidence intervals are uniformly most accurate. An exact method of calculating sample size to carry out one-sided tests (null hypothesis may involve a nonzero value for the multiple correlation coefficient) to attain a specified power is given. Sample size calculation for computing confidence intervals for the squared multiple correlation coefficient with a specified expected width is also provided. Sample sizes for powers and confidence intervals are tabulated for a wide range of parameter configurations and dimensions. The results are illustrated using the empirical data from Timm (1975) that related scores from the Peabody Picture Vocabulary Test to four proficiency measures.

Molecular discrimination inside polymer nanotubules

Recognition of small organic molecules and large biomolecules such as proteins is of great importance in pharmaceutical as well as biological applications. Recognition inside a nanoporous membrane is particularly attractive, because of the advantages associated with ligand-receptor interactions in confined spaces. Classical nanoporous membrane-based separations simply use the difference in size of the analytes relative to pore size in the membrane. In order to bring about selectivity beyond size, it is necessary that methods for functionalizing the membrane pores are readily available. Here, we describe a simple approach to functionalize the nanopores within these membranes using self-assembling and non-self-assembling polymers. We show that these modified membranes separate small molecules based on size, charge and hydrophobicity. We also demonstrate here that proteins can be differentially transported through the nanopores based on their size and/or electrostatics.

Statistical methods for establishing equivalency of several sampling devices

The problem of comparing several alternate sampling devices to the Occupational Safety and Health Administration (OSHA) standard, or the comparison of several sampling devices among themselves, is considered. A test based on the OSHA criterion that states that "90% of the readings of the sampling device should be within +/- 25% of the readings obtained by the standard" is developed. Type I error rates and powers of the test are studied using Monte Carlo simulation. The study indicates that the proposed test is quite satisfactory for applications. The method is illustrated using a simulated data set.

Transmission dynamics of diurnally subperiodic lymphatic filariasis transmitted by Ochlerotatus (Finlaya) niveus in the Andaman & Nicobar Islands

BACKGROUND & OBJECTIVE

In India diurnally subperiodic filariasis is prevalent only in the Nicobar district of Andaman and Nicobar Islands, with significant health problem. Sample surveys indicated that this form of filariasis is restricted to a small region of Nancowry group of islands with Ochlerotatus niveus as the vector. We therefore carried out a comprehensive study to assess the transmission dynamics of LF in Teressa island in Nicobar district in view of its control and evaluation of interventions.

METHODS

Entomological studies were carried out for a period of twelve months covering all the seasons in the year, by means of man landing catches in Teressa Island, an endemic island for this form of filariasis. Parameters viz., the annual biting rate (ABR), annual infective biting rate (AIBR), annual transmission index (ATI), risk of infection index (RII) and annual transmission potential (ATP), which reflect the dynamics and intensity of transmission of filariasis, were estimated. Host efficiency of Oc. niveus was also assessed.

RESULTS

The number of vectors biting a person in a year was estimated to be 21851, of which 107 were harbouring infective parasite. Risk of infection intensity was 0.02332. Every person in this study area was at the risk of receiving an estimated number of 22 infective stage larvae per year. The host efficiency index of Oc. niveus indicated that over 40 per cent of the microfilariae ingested were able to develop into infective stages. The ATP was 169 with evidence of year round transmission. The pattern of monthly transmission potential suggested that the intensity of transmission was high during summer months.

INTERPRETATION & CONCLUSION

Perennial transmission of subperiodic Wuchereria bancrofti in the typical forest ecosystem was evident in Teressa Island with transmission parameters suggesting that summer is a high risk season for transmission. Personal protection measure is the method of choice to protect from the risk of infection, because of day biting, exophilic and exophagic behaviour of the vector and larvae are not amenable to larvicidal measures. An alternative method to control the transmission would be to use selective or periodic mass chemotherapy to reduce the parasite load in this community.

Health Related Quality of Life, an appropriate indicator to assess the impact of morbidity management and disability prevention activities towards elimination of lymphatic filariasis

Background

Lymphatic filariasis has been identified as one of the six diseases that can be potentially eliminated. Global programme to eliminate lymphatic filariasis has been launched, applying principal strategies of mass drug administration to interrupt transmission and morbidity management to prevent disability. The strategy for mass drug administration has been clearly laid out and guidelines have been well documented for implementation, monitoring and evaluation of the programme but such a guideline is warranted for morbidity management and disability prevention activities.

Discussion

Health Related Quality of Life, a multidimensional construct referring to patients' perceptions of the impact of disease and treatment on their physical, psychological and social function and well being is crucial in the evaluation of health care interventions. Lymphatic filariasis has a wide clinical spectrum and disability is more pronounced in the advanced stages of lymphoedema and hydrocele. Since the advanced stages of lymphoedema are not reversible, morbidity management and disability prevention activities can lessen the disabilities due to secondary infections and there by improve the quality of life of the patient. Thus, an improvement in quality of life is considered to be important as a primary outcome in the determination of therapeutic benefit. Therefore it can be used as an indicator to assess the impact of morbidity management and disability prevention activities in global programme to eliminate lymphatic filariasis.

Summary

Disease specific Health Related Quality of Life instrument can be used to measure the longitudinal changes in quality of life of patients following the intervention. High responsiveness, clinical relevance to patients and its sensitiveness to detect small changes are the merits of disease specific instrument. Morbidity management and disability prevention activities under filariasis elimination programme aim at improving the quality of life of patients with irreversible manifestations. Therefore there is an urgent need to develop an instrument to assess the health related quality of life, specific for lymphatic filariasis by incorporating all the difficulties and problems caused to patients by the disease in the physical, mental and social domains of health.

School-based health education campaign--a potential tool for social mobilization to promote the use of DEC-fortified salt towards elimination of lymphatic filariasis

Community compliance is crucial for the success of mass treatment using cooking salt fortified with diethylcarbamazine citrate (DEC) for the elimination of lymphatic filariasis (LF). We describe the role and effectiveness of school-based health education for social mobilization to promote the use of DEC salt, in an endemic district in India. Health education through classroom sessions was the main motivational strategy used. Community members were targeted to receive the message through children. The impact of this approach was assessed among students and community members using an interviewer-administered questionnaire and analysis of salt samples for DEC content from households. Significant improvement in awareness on LF among students and community respondents was observed. School health education (SHE) could promote the use of DEC salt by 19% points more in households with children in schools covered under health education campaign [campaign school (CS)] compared with others. Significantly higher proportion (72.7%) of samples from households with children in CS had detectable DEC, indicating the impact of the intervention on enhancing the use of DEC salt by the community. The results exemplify that SHE is a potential tool for improving and sustaining compliance, thus serving as part of a public health strategy to eliminate LF using DEC salt.

Upper limits for exceedance probabilities under the one-way random effects model

In this article, we propose statistical methods for setting upper limits on (i) the probability that the mean exposure of an individual worker exceeds the occupational exposure limit (OEL) and (ii) the probability that the exposure of a worker exceeds the OEL. The proposed method for (i) is obtained using the generalized variable approach, and the one for (ii) is based on an approximate method for constructing one-sided tolerance limits in the one-way random effects model. Even though tolerance limits can be used to assess the proportion of exposure measurements exceeding the OEL, the upper limits on these probabilities are more informative than tolerance limits. The methods are conceptually as well as computationally simple. Two data sets involving industrial exposure data are used to illustrate the methods.

A MULTIVARIATE TEST FOR SIMILARITY OF TWO DISSOLUTION PROFILES

A multivariate test of size a for assessing the similarity of two dissolution profiles is proposed. The inferential procedure is developed by using the approach for the common mean problem in a multivariate setup due to Halperin (1961). The performance of the proposed method is compared with Intersection Union Test as well as f2 criterion recommended by the FDA through a simulation study. All the methods are illustrated with real examples.

Probing the periphery of dendrimers by heterogeneous electron transfer

The accessibility of the electroactive periphery was studied and compared for dendrimers and linear analogs by heterogeneous electron transfer using microelectrodes.

On Selecting Tests for Equality of Two Normal Mean Vectors

The conventional approach for testing the equality of two normal mean vectors is to test first the equality of covariance matrices, and if the equality assumption is tenable, then use the two-sample Hotelling T (2) test. Otherwise one can use one of the approximate tests for the multivariate Behrens-Fisher problem. In this article, we study the properties of the Hotelling T (2) test, the conventional approach, and one of the best approximate invariant tests (Krishnamoorthy & Yu, 2004) for the Behrens-Fisher problem. Our simulation studies indicated that the conventional approach often leads to inflated Type I error rates. The approximate test not only controls Type I error rates very satisfactorily when covariance matrices were arbitrary but was also comparable with the T (2) test when covariance matrices were equal.

Generalized P-values and confidence intervals: a novel approach for analyzing lognormally distributed exposure data

The problem of assessing occupational exposure using the mean of a lognormal distribution is addressed. The novel concepts of generalized p-values and generalized confidence intervals are applied for testing hypotheses and computing confidence intervals for a lognormal mean. The proposed methods perform well, they are applicable to small sample sizes, and they are easy to implement. Power studies and sample size calculation are also discussed. Computational details and a source for the computer program are given. The procedures are also extended to compare two lognormal means and to make inference about a lognormal variance. In fact, our approach based on generalized p-values and generalized confidence intervals is easily adapted to deal with any parametric function involving one or two lognormal distributions. Several examples involving industrial exposure data are used to illustrate the methods. An added advantage of the generalized variables approach is the ease of computation and implementation. In fact, the procedures can be easily coded in a programming language for implementation. Furthermore, extensive numerical computations by the authors show that the results based on the generalized p-value approach are essentially equivalent to those based on the Land's method. We want to draw the attention of the industrial hygiene community to this accurate and unified methodology to deal with any parameter associated with the lognormal distribution.