Table 1 Percentage of self-reported non-smokers having urinary cotinine higher than 6.6 mmol/ml by socio-demographic groups and smoking status Percentages Probabilities P o s t S c r i p t LETTER Validity of self-reported smoking among women hospital staff in Tunisia In Tunisia, smoking prevalence is high1 (55.6% males vs 5.2% females).2 However, under- reporting of smoking may occur, particularly among women from cultures where social proscriptions still exist.3 No studies on women’s smoking have been published in Tunisia which have validated self-reported smoking with biomarkers such as urinary cotinine.4 We aimed to assess the validity of self- reported smoking among female staff in a Tunisian hospital. Our data were extracted from a cross- sectional study5 conducted between January and May 2005 to assess smoking behaviours of the health professional staff at Charles Nicolle Hospital in Tunis, the largest University Hospital in Tunisia. About 1120 women were involved in the study and 809 (73%) provided a urine sample. The rate of participation did not differ signiﬁcantly according to age, occupa- tional group or self-reported smoking status. An anonymous questionnaire was adminis- trated. The ‘smokers’ category includes current smokers. Ex-smokers were those who had smoked at least 100 cigarettes in their life but were no longer smoking. The quantitative colorimetric urine test is based on the könig reaction, in which pink-red chromophores formed from nicotine and its metabolite condensates with barbituric acid were extracted into an acetate buffer. As for the analytic condition, an aliquot of urine sample(0.5 ml) was mixed with 0.2 ml of 4 M acetate buffer (pH 4.7), with 0.1 ml of KCN (1%) and then 0.5 ml of barbituric acid (10%). The measurable time was deﬁned as 45 min duration and absorbance at 510 nm. Data were analysed by SPSS Version 16 using a Student’s t test and c2 test. The signiﬁcance threshold was 5%. Among women who self-reported as smokers, 72.7% had a cotinine concentration of cut-off 6.6 mmol/ml (table 1). Among self- reported ex-smokers and non smokers, 19.4% and 10% of women, respectively, had coti- nine in their urine at the cut-off level. The validity of self-reported smoking was similar among subjects from different areas, ages and occupational group categories (table 1). Non-smokers exposed to environmental tobacco smoke from other household members and friends may have cotinine in urine; however, the rate is typically below 6.6 mmol/ml.6 7 If we assume that all women who tested positive smoke daily or occa- 86 Tobacco Control January 2011 Vol 20 No 1 Variables Professional category <Physiciansepharmacists, administrators (n¼121) <Nurses (n¼418) <Blue workers (n¼130) Area <Urban (n¼510) <Suburban (n¼131) <Rural (n¼41) Age group <20e29 years (n¼190) <30e39 years (n¼205) <>¼40 years (n¼286) Self-reported smoking status <Current smokers (n¼55) <Occasional smokers (n¼21) <Ex-smokers (n¼31) <No smokers (n¼689) sionally, the percentage of smokers increases from 9.5% to 18.4%. Self-reports of smoking are accurate in most studies in high-income countries,8 but may be under-reported in low- and middle-income countries, particu- larly in female and adolescents. For example, the prevalence of self-reported smoking among Iranian men and women aged 19 years and above was 18.7% and 1.3%, respectively, compared to 21.2% and 6.7% based on serum cotinine level.9 The study has some limitations. It was conducted among women in the health profession who are subject to both socio- cultural and professional pressures explaining the under-reporting of smoking status. In addition, since this study involved health professionals in a university hospital in the capital, our results cannot be gener- alised to all health professionals in the country. Radhouane Fakhfakh,1 Anis Klouz,2 Mohamed Lakhal,2 Chalbi Belkahia,2 Noureddine Achour1 1National Institute of Public Health, Tunisia; 2Centre National de pharmaco-vigilance Tunis, Tunisia Correspondence to Radhouane Fakhfakh, National Institute of Public Health, 5-7 Rue Khartoum imm le Diplomat, 1002 Le Belvedere Tunis, Tunisia; radhouane.fakhfakh@rns.tn Funding This research was supported by Tunisian Ministry of High Education and Scientiﬁc Research, Unity of Research on Tobacco Epidemiology and Control. Competing interests None. Provenance and peer review Not commissioned; externally peer reviewed. Accepted 5 August 2010 Published Online First 29 September 2010 11.1% 10.0% 12.8% 11.3% 09.4% 04.7% 13.4% 10.3% 07.8% 72.7% 14.3% 19.4% 10.0% NS NS NS <0.0001 Tobacco Control 2011;20:86. doi:10.1136/tc.2010.038661 This paper is freely available online under the BMJ Journals unlocked scheme, see http://tobaccocontrol. bmj.com/site/about/unlocked.xhtml REFERENCES 1. 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