You will be presented with the full text of a biomedical research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
insulin resistance ( ir ) is an important factor in the pathophysiology of type  2 diabetes and metabolic syndrome , and the homeostasis model assessment of ir ( homair ) has been widely used in numerous epidemiological studies .
although reference intervals are the most commonly used means for assessing and interpreting clinical laboratory results , reference intervals for homair have not been clearly established . as diagnostic specificity and sensitivity
are affected by the validity of the reference interval , the c28a3 document has been recommended by the clinical and laboratory standards institute ( clsi ; formerly the national committee for clinical laboratory standards ) for appropriate statistical determination of reference intervals . based on this document ,
reference intervals are to be determined by : ( i ) selection of a minimum of 120 healthy reference individuals using appropriately defined criteria ; ( ii ) normalization of the data for parametric analysis ; ( iii ) truncation of data for outlier rejection ; and ( iv ) establishment of the reference interval between the 2.5th and 97.5th percentiles of the reference distribution .
the aim of the present study was to determine an optimal reference interval for homair in a japanese population based on the clsi c28a3 document .
among 5297 healthcheck examinees who first visited the health evaluation and promotion center at tokai university hachioji hospital between april 2007 and march 2010 , we excluded 962 subjects receiving medication for hypertension , dyslipidemia or diabetes and those with a history of coronary artery disease , cerebrovascular disease or chronic renal failure . among the remaining 4335 subjects , 2173 subjects aged 2079 years with fasting plasma glucose ( fpg ) 
<  100  mg / dl , body mass index ( bmi )  <  25  kg / m and alanine aminotransferase ( alt )  <  31  u / l were selected as reference individuals .
all measurements were included in the routine healthcheck examinations and anonymized health records were used for analysis .
the present study was designed in compliance with the ethics regulations outlined in the helsinki declaration , and the privacy of participants was protected by unlinkable anonymization .
liver enzymes were measured following the standardized procedure by the japan society of clinical chemistry .
fasting serum immunoreactive insulin ( iri ) was measured by fluorescenceenzyme immunoassay ( st aiapack iri ; toso , tokyo , japan ) .
the intra and interassay coefficients of variation were 1.42.3 and 2.64.6% , respectively , and crossreactivity with proinsulin molecules was 2.0% .
homair was calculated as : fpg ( in mg / dl )    iri ( in mu / ml)/405 .
normality was examined using the shapiro  wilk test . because the data for homair did not adhere to a gaussian distribution , logtransformed values ( log homair ) were used .
log homair values outside of mean    3 standard deviations ( sd ) were truncated as outliers .
we then calculated mean   2  sd of log homair values , which covers the central 95% of the population .
spss statistics version 18.0 software ( spss , chicago , il , usa ) was used for all statistical analyses .
the prevalence of hypertriglyceridemia ( triglyceride    150 mg / dl ) and hypertension ( systolic blood pressure    140  mmhg or diastolic blood pressure    90  mmhg ) was 6.1 and 6.2% , respectively ( table  1 ) .
homair showed a clear rightskewed shift from the gaussian distribution ( figure  1a ) .
log homair appeared more normally distributed , although the normality was not statistically significant ( figure  1b ) .
after outlier rejection , we calculated mean    2  sd of log homair values ( figure  1c ) .
inverse transformation of log homair values corresponding to mean    2  sd yielded the reference limits for homair of 0.4 and 2.4 .
there was little difference in homair among different age groups ( 0.42.4 for those aged 2029 , 3039 , 4049 and 5059  years ; 0.42.3 for those aged 6069  years ; and 0.32.2 for those aged 7079  years ) .
alt , alanine aminotransferase ; ast , aspartate aminotransferase ; bmi , body mass index ; bp , blood pressure ; firi , fasting immunoreactive insulin ; fpg , fasting plasma glucose ; gt , glutamyl transpeptidase ; hdlc cholesterol , highdensity lipoprotein cholesterol ; homair , homeostasis model assessment of insulin resistance ; ldlc , lowdensity lipoprotein cholesterol ; tg , triglyceride . 
( a ) homeostasis model assessment of insulin resistance ( homair ) in reference individuals ( n  =  2173 ) .
( c ) after truncation of log homair values outside of the mean    3  sd , mean    2  sd of log homair was calculated for 2153 subjects .
to the best of our knowledge , this represents the first reference interval study of homair following the stringent clsi c28a3 document .
decisionbased , defining specific medical decision limits for use by clinicians to diagnose or manage patients .
the present study attempted to establish a healthassociated interval for homair , and selected reference individuals based on criteria of freedom from chronic disorders requiring regular medication , aged 2079  years , fpg  <  100 mg / dl , bmi 
<  25  kg / m and alt  <  31  u / l .
although elderly subjects are known to be insulin resistant , there was little difference in homair among different age groups .
we excluded subjects with fpg    100  mg / dl based on the latest global definition of metabolic syndrome .
subjects with bmi    25  kg / m were excluded , because ir is strongly associated with obesity .
furthermore , subjects with alt    31  u / l were excluded because alt is often used as a surrogate marker for fatty liver , which is associated with increased fasting insulin secondary to hepatic ir or decreased hepatic insulin clearance .
although we excluded subjects receiving medication , bias from the inclusion of undiagnosed hypertriglyceridemia and hypertension might be a concern .
the japan diabetes society has recommended homair    1.6 as indicating nonir and homair    2.5 as identifying ir in their  treatment guide for diabetes 2010. however , homair    1.6 as nonir was described by only one japanese report , which used the 90th percentile of absolute homair .
there have been no studies showing the validity of homair    2.5 as ir , even though homair    2.5 has often been used in asian studies .
the present study showed an upper reference limit for homair of 2.4 , so defining homair    2.5 as indicating ir appears reasonable .
several reports have determined upper limits for homair of 1.7 , 1.73 , 1.97 and 2.0 in japanese populations .
average bmi ranged from 21.221.6  kg / m across these reports , similar to that in the present study .
shimomura et  al . used mean  +  1  sd of absolute homair values , whereas nakai et al . and matsumoto et  al .
however , none of the studies stringently complied with the guideline in terms of selecting reference individuals , normalization and truncation of data , or interval settings . if we define ir using the upper 90 percentile , the threshold value can be calculated as 1.7 in our reference individuals .
again , there is no rationale for using the 90th percentile for appropriate statistical determination .
few studies have examined homair reference limits in nonasian populations . in an italian study ,
2.77 was determined based on the lower limit of the top quintile of homair distribution in subjects with no apparent metabolic disorders ( n  =  888 , aged 4079  years , and mean bmi  <  25  kg / m ) .
a small spanish study of subjects without diabetes ( n  =  97 , average bmi 22.2  kg / m ) proposed homair  =  3.8 as the diagnostic criterion for ir using the upper 90 percentile . a populationbased study in the usa using an appropriate reference population and interval setting showed an upper reference limit for homair of 4.39 among american adolescents ( average bmi 24 
the extent of ir might differ between japanese and caucasians , and heterogeneity in ethnicity might contribute to discrepancies in the degree of ir among different ethnic groups .
however , it is unreasonable to directly compare those studies unless homair reference limits are determined by a standardized procedure . in conclusion ,
the present study is the first to establish a reference interval for homair by applying the stringent clsi c28a3 document .
we have established the reference interval for homair as between 0.4 and 2.4 , and homair    2.5 can be considered a reasonable indicator of ir in japanese subjects .
abstractthe aim of the present study was to establish a reference interval for homeostasis model assessment of insulin resistance ( homair ) in a japanese population based on the c28a3 document from the clinical and laboratory standards institute ( clsi ) . 
 we selected healthy subjects aged 2079  years , with fasting plasma glucose  <  100  mg / dl , body mass index  <  25  kg / m2 and alanine aminotransferase  
 <  31  u / l . 
 homair values were log transformed , values beyond mean    3 standard deviations ( sd ) were truncated , and the mean    2  sd of log homair values were taken as the upper and lower reference limits of homair . 
 we selected 2173 subjects as reference individuals , and 2153 subjects were used for analysis . 
 the reference interval for homair was established as between 0.4 and 2.4 . 
 this represents the first reference interval study for homair that applies the stringent clsi c28a3 document . 
 homair 
   2.5 should be considered a reasonable indicator of insulin resistance in japanese . 
 ( j diabetes invest , doi : 10.1111/j.20401124.2011.00113.x , 2011 )