mesothelioma is an uncommon , malignant neoplasm that arises from mesothelial tissue usually in the pleura , less often in the peritoneum , and rarely elsewhere . prognosis for malignant mesothelioma ( mm ) is poor , and the tumor has a median latency period of 32 years from the time of exposure to causative agents [ 1 , 2 ] . exposure to asbestos is considered the most important cause of mm [ 3 , 4 ] . in diseases with potential occupationally or environmentally related causes , such as mesothelioma , once diagnosed , the median length of survival for persons with mm varies from 5.9 to 11 months [ 57 ] . the ability to interview persons with newly diagnosed mm is limited because of the very short survival period . proxy interviewing is a commonly used method of obtaining information on persons with rapidly fatal diseases [ 8 , 9 ] . however , some studies have shown that data received from proxies may be inaccurate or require the review of additional information sources [ 1012 ] . for this investigation , we collected data on the persons potential direct or indirect occupational and environmental exposure to asbestos , genetic , and health related malignancy predisposition , and exposure to tobacco products which does not cause mesothelioma by itself but may complicate the person 's chances of contracting a disease . we collected this information from both the person with mm and a family member designated as his or her proxy . mm was defined as an international classification of disease ( icd ) oncology ( icd-9 and icd-10 ) histology codes 9050 through 9053 . persons with mm diagnosed in 2002 through 2005 in new york and new jersey and 19972004 in wisconsin were eligible for inclusion in the project . additionally , in new york and new jersey , names , phone numbers , and addresses of persons with newly diagnosed mesothelioma were collected through monthly visits and phone calls to hospitals where the majority of mesothelioma patients were observed and treated . as soon as persons with mm were identified and were determined to be alive , we contacted their physician to obtain the written or verbal consent to contact his / her patients . if consent was received , we sent an introductory letter inviting them to participate in this investigation . then we contacted them by phone to obtain verbal consent and interview . during the interview , we asked them to identity a family member they knew them best and who could give the most detailed information in a proxy interview . at a later point in time , which varied , the proxies gave verbal consent and were interviewed . the interview focused on the respondents ' and their family 's exposure history and medical history , and respondents ' smoking history . the environmental protection agency ( epa ) list of jobs / activities potentially associated with exposure to asbestos was adapted for this project to assess the exposure history . there were a total of 77 questions on five topics ; 73 of these questions for which paired responses were a dichotomous  yes  or  no ,  were analyzed . pairs where one or both respondents had missing ,  do n't know  or  refused analysis included 15 case exposure history questions , 24 case medical history questions , 14 family exposure history questions , 13 family medical history questions , and 7 smoking history questions . the relationship of the proxy to the case was categorized as spouse , child , sibling , or other ( mostly parents ) . to evaluate the response differences , we stratified the response data by the relationship subgroups during the analysis . in 1947 , mcnemar introduced a test for matched - pair data with a dichotomous response . since then , this test has become a commonly used method for analyzing paired binary response data as correlated proportions . in our analysis , these procedures refer to the case and the proxy , respectively . the mcnemar test assumes independence among the paired responses . our study evaluated matched - pair responses to five topics . each case / proxy pair contributed more than one paired binary response to each topic . therefore , the independence assumption no longer existed , and application of the mcnemar test could result in inflating paired responses and underestimating standard error . this adjusted mcnemar test allows testing the agreement of multiple paired responses between the respondents and their proxy with no inflated information . the adjusted chi - square value , [ v ] was calculated as 
 ( 1)v2=(k=1k(bkck)/nk)2k=1k[(bkck)/nk]2 , 
 where bk = j=1bjk and ck = j=1cjk , and bjk , cjk = 0 or 1 for all j questions in the kth matched - pair responding . the nk is the valid count of paired binary response . the bk and ck are the summation of the two types of discordant of bjk and cjk , respectively . we used the mcnemar / durkalski test to adjust the correlated multiple paired responses on each topic . the null hypothesis of this test is that the two marginal probabilities are the same ; that is , there is no difference between the responses from matched pairs . the data were analyzed using sas version 9.3.1 analytical software ( cary , nc ) . total of 33 paired interviews ( eight paired interviews in new jersey , ten paired interviews in new york , and 15 paired interviews in wisconsin ) were collected . respondents were mostly white males , not of hispanic or latino origin , married , and over 60 years old with a high school or college pregraduate education . respondent medical and family medical questions were the most difficult to answer with 3.8% and 4.2% unknown / missing , respectively . spouses performed the best in exposure questions ( 89.8% agreement ) and respondent and proxy medical history questions ( 94.1% and 90.0% agreement accordingly ) . however , the mcnemar / durkalski test discovered no statistically significant heterogeneity between paired responses regardless of relationship and the question 's topic . the only exception was a chi - square value 5.57 ( p = 0.02 ) for smoking history , showing statistically significant disagreement between paired responses . this was statistically significant only for spouses ( chi - square value 5.91 , p = 0.02 ) , although they answered the same percent of questions correctly as siblings and parents . of the 33 paired interviews obtained from new jersey , new york , and wisconsin , we generally found agreement across the topics regardless of the familial relationship . however , the larger number of spouses in the cohort contributed to the statistical significance . the real percent disagreement was not really that much more for spouses than for other subgroups of proxies . the generally high ability of surrogate responders to give interviews of comparable quality and completeness of exposure data was reported by nam et al . , pickle et al . , and cordiero . similar results were found by campbell et al . , who applied the polytomous logistic regression models analyzing the utility of proxy versus index respondent information in a population - based case - control study of rapidly fatal cancers . polytomous logistic regression models found only a few examples of meaningful heterogeneity among all variables including the cigarette smoking model . the biggest limitation of this study was the small number ( 33 ) of paired interviews available for the analysis . for example , we may speculate that siblings and others that have borderline p values for each question group might show significant difference with a larger number of pairs . the interpretation of results with regard to the accuracy of proxy interviews could be affected by the biased nature of the sample . additionally respondents may have had a somewhat longer survival from time of diagnosis than those not able to participate , perhaps because they were younger or had a stronger social support network of relatives . in addition , other factors , such as pending litigation and communication between pairs about the interview , may affect the accuracy . the more detailed multilevel responses were not analyzed because they did not show good agreement or were difficult to meaningfully compare answers . obtaining exposure information on persons with rapidly fatal diseases such as mm and other aggressive malignancies requires using alternative methods of collecting information about risk factors . our study indicates that family proxy interviews , using dichotomous responses , can serve as an acceptable source of information about health and exposure - related risk factors for mm . the reliability of information received from proxies was generally high but varied by topic and familial relationship , all of which need to be taken into consideration , particularly in diseases strongly associated with smoking . although the number of pairs available for analysis was small , these data suggests proxy interviews adequately answered big - picture questions regarding exposure . future studies should explore whether more accurate information can be obtained through the use of interviews with multiple proxies per case .