the world health organization has defined health literacy ( hl ) as  the cognitive and social abilities which determine the incentive and ability of individuals to increase access to understand and use information in ways , which promote and preserve good health . 
the hl of patients has obtained more attention as a risk factor for poor adherence to treatment and adverse outcomes in chronic disease 's management particular in diabetes care .
diabetes is the most common metabolic disease with a dramatic increase rate of prevalence throughout the world , which has an important impact on the public health and quality of life of the patients .
there is a developing frame of the literature that discovers the association between hl and health outcomes in people with diabetes .
older studies of low hl reported adverse effects on diabetes - related health outcomes ; however , more recent studies showed no association between hl levels and intensity , frequency or incidence of outcomes , and thus the effect of hl on the health of people with diabetes is yet unclear .
based on national reports , the prevalence of diabetes has been raised during three decades in iran and also a recent national survey about hl has shown that majority of people has inadequate knowledge .
however , there are different tools to measure hl and numeracy skills in general population in different languages , only diabetes numeracy test-15 ( dnt-15 ) has been developed specifically to measure numeracy skills in patients with diabetes as first scale by huizinga et al .
, in english language . with regard to lacking of appropriate measurement tool for patients with diabetes in persian ( farsi ) language , this study aimed to provide evidence for the psychometric properties of the iranian ( persian language ) version of dnt-15 .
the dnt was designed to evaluate nutrition , exercise , glucose monitoring , oral medication , and insulin skills that patients may encounter during daily diabetes self - management .
blood - glucose monitoring skills are evaluated by three items about number hierarchy , glaciated hemoglobin , and calculating supplies needed .
eight items assess the oral medication use and insulin use . oral medication ( one question )
use refill patterns and dates , and oral titration schemes and insulin use ( seven questions ) including interpretation of syringes , correction or sliding - scale insulin use , insulin adjustment for carbohydrate intake , and titration instructions [ table 1 ] .
items are scored as binary outcomes  correct or incorrect  and no partial credit is given .
many patients with diabetes use calculators ; therefore , participants were allowed to use calculators during the administration of the dnt to emulate real - life circumstances .
dnt scores are reported as percent correct ( with a possible range of 0% to be 100% ) .
description of diabetes numeracy test items in this phase , the original questionnaire was translated by two independent health professionals from english to persian .
after translation , by consultation with the principal investigators , the results were rechecked . finally , they achieved a precision translation for the questionnaire . in this phase ,
the questionnaire that translated in the previous step , gave to two professional translators whose native language were english , and they are sufficient dominance in persian language .
the translators did not communicate with one another and did not know the original english version .
translated versions by consultation with the principal investigators of conversion backward translation were combined . in this phase ,
a group of experts was reviewed , all phases , including verification and cross - cultural equivalent ( cross - cultural equivalence ) .
cultural equivalent to the word ( semantic ) , a term equivalent ( idiomatic ) , and equivalent experience ( experiential ) , and conceptually equivalent ( conceptual ) were performed by an expert panel .
this group included experts in diabetes , certified diabetes educators , methodologist , primary care providers , and registered dietitians , behavioral researchers in diabetes , and literacy and numeracy experts . finally , the dnt was to address the clarity of items for patients with diabetes .
interviewees were asked specific questions about each item to evaluate the understandability of the wording .
if an item was unclear , the interviewee was told the purpose of the item and then encouraged to suggest a different format or wording . in response to the interviews , the scale was reformatted and slightly reduced to the final 15-items .
reliability was evaluated by internal consistency ( kuder - richardson 20 ) , and validity was evaluated through content validity ratio ( cvr ) and content validity index ( cvi ) .
a convenience sample of 120 patients with diabetes was interviewed in the diabetes clinic affiliated to institute of endocrinology and metabolismof an item at clinic visits . any person diagnosed with type 1 and or type 2 diabetes which was able to read ( at least eight grades ) and speak persian language .
potential participants were excluded if they corrected visual acuity was > 20/50 using a rosenbaum pocket vision screener , or if they had a diagnosis of significant dementia , psychosis , or blindness .
the dnt was designed to evaluate nutrition , exercise , glucose monitoring , oral medication , and insulin skills that patients may encounter during daily diabetes self - management .
blood - glucose monitoring skills are evaluated by three items about number hierarchy , glaciated hemoglobin , and calculating supplies needed .
eight items assess the oral medication use and insulin use . oral medication ( one question )
use refill patterns and dates , and oral titration schemes and insulin use ( seven questions ) including interpretation of syringes , correction or sliding - scale insulin use , insulin adjustment for carbohydrate intake , and titration instructions [ table 1 ] .
items are scored as binary outcomes  correct or incorrect  and no partial credit is given .
many patients with diabetes use calculators ; therefore , participants were allowed to use calculators during the administration of the dnt to emulate real - life circumstances .
dnt scores are reported as percent correct ( with a possible range of 0% to be 100% ) .
in this phase , the original questionnaire was translated by two independent health professionals from english to persian .
in this phase , the questionnaire that translated in the previous step , gave to two professional translators whose native language were english , and they are sufficient dominance in persian language .
the translators did not communicate with one another and did not know the original english version .
in this phase , a group of experts was reviewed , all phases , including verification and cross - cultural equivalent ( cross - cultural equivalence ) .
cultural equivalent to the word ( semantic ) , a term equivalent ( idiomatic ) , and equivalent experience ( experiential ) , and conceptually equivalent ( conceptual ) were performed by an expert panel .
this group included experts in diabetes , certified diabetes educators , methodologist , primary care providers , and registered dietitians , behavioral researchers in diabetes , and literacy and numeracy experts . finally , the dnt was to address the clarity of items for patients with diabetes .
interviewees were asked specific questions about each item to evaluate the understandability of the wording . if an item was unclear , the interviewee was told the purpose of the item and then encouraged to suggest a different format or wording . in response to the interviews , the scale was reformatted and slightly reduced to the final 15-items .
reliability was evaluated by internal consistency ( kuder - richardson 20 ) , and validity was evaluated through content validity ratio ( cvr ) and content validity index ( cvi ) .
a convenience sample of 120 patients with diabetes was interviewed in the diabetes clinic affiliated to institute of endocrinology and metabolismof an item at clinic visits . any person diagnosed with type 1 and or type 2 diabetes which was able to read ( at least eight grades ) and speak persian language .
potential participants were excluded if they corrected visual acuity was > 20/50 using a rosenbaum pocket vision screener , or if they had a diagnosis of significant dementia , psychosis , or blindness .
difficult issues for participants included titration schemas , food label interpretation , insulin adjustment instructions , and items that required multi - step math ( e.g. , calculating insulin dosage based on carbohydrate intake and glucose level ) .
questions 2 , 5 , 6 , 7 , 8 , 9 , and 11 were answered accurately respectively by 89.1% , 78.2% , 87.4% , 72.3% , 85.7% , 84% , and 83% of participants for this study .
however , questions 14 and 15 , which required patients to interpret a word problem and apply multiple numerical steps to determine their insulin dosage , was only answered correctly , respectively by 41% , 54% of the participants .
the 15-item persian version of the dnt has highly reliable , as determined by internal consistency kuder - richardson ( kr-20 = 0.90 ) .
content validity was examined by the expert panel ( cvr : 089 and cvi : 0.86 ) .
the short version of the dnt-15 demonstrated internal consistency and construct validity in relation to reading skills in persian ( farsi ) language in iranian population .
scores on the dnt-15 showed a direct correlation with level of education in this study which is consistent with other reports .
although there have been some reports about hl in iran they were not specific about diabetes in iran .
other studies have identified the role of hl techniques in the improvement of health outcomes in diabetes and congestive heart failure .
patients with low hl may benefit from interventions that address numeracy , particularly in the setting of diabetes management .
the dnt-15 can provide a measurement of diabetes - specific numeracy and provide more information on the role of disease - specific numeracy in future studies .
more studies are needed to further understand the role of numeracy tailored interventions for the management of diabetes .
for example , study participants had a difficult time with the multi - step math required to calculate a correction dosage of insulin when instructions were presented as a sequence of sentences .
this item was encompassed to mirror clinical practice regarding how patients are currently instructed to take their insulin .
this example provides an important lesson for health care providers and educators in effective communication styles for all clinical care recommendations .
the persion ( farsi ) version of dnt-15 is a reliable and valid tool to measure of diabetes - specific numeracy skills for patients with diabetes .
 background : low health literacy ( hl ) of patients has obtained more attention as a risk factor for poor adherence to treatment and adverse outcomes in chronic disease 's management particular in diabetes care . 
 diabetes numeracy test-15 ( dnt-15 ) has been developed specifically for this purpose . 
 the objective of the current study is to evaluate psychometric properties of iranian ( persian ) version of the dnt-15.methods:the shortened version of the dnt ( 15-items ) was completed by 120 patients with diabetes . 
 the kuder  
 richardson formula 20 for internal consistency was conducted . 
 content validity , criterion - related validity , and construct validity were also evaluated.results:the average score on the dnt was 72% and took an average of 25 minutes to complete . 
 the dnt-15 had a very good internal reliability ( kr-20 = 0.90 ) and also content validity ( content validity ratio : 089 and content validity index : 0.86).conclusions : the dnt-15 ( persian version ) is a reliable and valid measure of diabetes - related numeracy skills for iranian patients with diabetes ; however , additional studies are needed to further explore the association between diabetes - specific numeracy and acculturation and their impact on diabetes - related outcomes in iranian population . 