A point-of-care cassette test for detection of Strongyloides stercoralis.

Strongyloides stercoralis is a parasite that causes strongyloidiasis worldwide. It may lead to a life-long infection in immunocompetent people and hyperinfection in immunosuppressed patients. A point-of-care (POC) rapid test is helpful for patient diagnosis in resource-limited settings and as a detection tool in elimination/control programs. Previously, we reported a rapid IgG4 dipstick test (Ss Rapid®) for Strongyloides suitable for a laboratory setting. A POC cassette format of the test, which is field-applicable, has since been developed. Here, we report on a laboratory-based evaluation of the Ss Rapid® cas sette test on 285 sera. We assessed the diagnostic sensitivity of the Ss Rapid® cas sette with 32 sera, comprising samples from larval and/or DNA positive individuals from three countries. Additionally, we also tested samples from 33 seropositive endemic areas residents. We evaluated the diagnostic specificity of the test using 220 samples, comprising sera from other infections (n = 101), allergy cases with high IgE antibodies (n = 4), and blood donors (n = 115). The test showed high diagnostic sensitivity (97%, 31/32), and all sera of the seropositive endemic residents were reactive. It also showed high diagnostic specificity (94.5%, 208/220), and all false-positive samples tested negative after sera adsorption using recombinant NIE-coated microsphere beads. Additionally, we showed that the test worked with spiked whole blood samples. The study results showed that the SsRapid® cas sette test merits further laboratory and field evaluations.

Seroprevalence of Strongyloides stercoralis among patients with leptospirosis in northern Iran: a descriptive cross-sectional study.

Strongyloidiasis and leptospirosis are neglected tropical diseases that have affected many countries across the world. In this study, we evaluated the seroprevalence of Strongyloides stercoralis among patients with leptospirosis in northern Iran. We evaluated 156 laboratory- or clinically confirmed leptospirosis cases. The overall seroprevalence of S. stercoralis was 32.0% (95% confidence interval (CI): 27.4-36.5%, 50/156). Seropositivity was significantly associated with agricultural activities (odds ratio (OR): 2.84, 95% CI: 1.0-8.77) and gastrointestinal disorders (OR: 2.4, 95% CI: 1.1-4.9). Laboratory findings indicated that seropositivity of S. stercoralis was significantly associated with decreased levels of platelet and elevated levels of creatinine, alanine aminotransferase and aspartate aminotransferase (P < 0.05). Our findings suggested a higher exposure to S. stercoralis larvae among patients with leptospirosis. The public health and medical communities may benefit from this research through preventive measures to improve farmers' knowledge and awareness regarding strongyloidiasis and leptospirosis and the associated risk factors.

Concurrent of blaCTX-M and blaNDM-1 genes in clinical isolates of Escherichia coli from northern Iran.

The emergence of E. coli producing extended-spectrum ß-lactamases and metallo ß-lactamases has been reported as an important cause of treatment failure. The present study aimed to evaluate the existence of blaCTX-M, blaTEM, blaSHV, blaNDM-1 and blaIMP1 genes among E. coli isolated from patients in Babol, Northern Iran. The pattern of antibiotic resistance and the prevalence of multidrug-resistant (MDR) E. coli isolates were determined. E. coli isolates were separated from clinical specimens and antimicrobial susceptibility test (AST) was performed using the disk diffusion method. These isolates were further evaluated for the production of ESBLs and MBLs enzymes using cefotaxime (CTX), ceftazidime (CAZ) disks with and without clavulanic acid, and two CAZ with 2 mercaptopropionic acid disks, respectively. The ESBLs and MBLs positive isolates were analysed for the existence of blaCTX-M, blaTEM, blaSHV, blaNDM-1 and blaIMP-1 genes with the conventional PCR method. Of 259 isolates, 117 ß-lactamase producing E.coli were detected. MDR isolates were observed in 110/117 (94.9%) E. coli. Among 117 isolates, ESBLs, MBLs and coproduction of ESBL and MBL enzymes were observed in 45, 7 and 65 isolates, respectively. PCR analysis showed that the predominant genes were blaCTX-M15(95.5%) and blaNDM-1 (31.9%) among ESBL and MBL producing E. coli, respectively. Also, the concurrent occurance of the blaCTX-M with blaTEM, blaSHV, blaNDM-1 and blaIMP-1 genes were demonstrated. In conclusion, high prevalence rate of MDR isolates, particularly ESBL and MBL producing E. coli, observed in the current study shows the necessity of control and management strategies for the aforementioned isolates. Also, the early detection of concurrent ESBLs and MBLs producing E. coli is necessary to avoid treatment failure and prevent the distribution of such bacteria.

Concurrent of blaCTX-M and blaNDM-1 genes in clinical isolates of Escherichia coli from northern Iran

@#The emergence of E. coli producing extended-spectrum β-lactamases and metallo β-lactamases has been reported as an important cause of treatment failure. The present study aimed to evaluate the existence of blaCTX-M, blaTEM, blaSHV, blaNDM-1 and blaIMP- 1 genes among E. coli isolated from patients in Babol, Northern Iran. The pattern of antibiotic resistance and the prevalence of multidrug-resistant (MDR) E. coli isolates were determined. E. coli isolates were separated from clinical specimens and antimicrobial susceptibility test (AST) was performed using the disk diffusion method. These isolates were further evaluated for the production of ESBLs and MBLs enzymes using cefotaxime (CTX), ceftazidime (CAZ) disks with and without clavulanic acid, and two CAZ with 2 mercaptopropionic acid disks, respectively. The ESBLs and MBLs positive isolates were analysed for the existence of blaCTX-M, blaTEM, blaSHV, blaNDM-1 and blaIMP-1 genes with the conventional PCR method. Of 259 isolates, 117 β-lactamase producing E.coli were detected. MDR isolates were observed in 110/117 (94.9%) E. coli. Among 117 isolates, ESBLs, MBLs and coproduction of ESBL and MBL enzymes were observed in 45, 7 and 65 isolates, respectively. PCR analysis showed that the predominant genes were blaCTX-M- 15(95.5%) and blaNDM-1 (31.9%) among ESBL and MBL producing E. coli, respectively. Also, the concurrent occurance of the blaCTX-M with blaTEM, blaSHV, blaNDM-1 and blaIMP-1 genes were demonstrated. In conclusion, high prevalence rate of MDR isolates, particularly ESBL and MBL producing E. coli, observed in the current study shows the necessity of control and management strategies for the aforementioned isolates. Also, the early detection of concurrent ESBLs and MBLs producing E. coli is necessary to avoid treatment failure and prevent the distribution of such bacteria.

Seroprevalence and molecular detection of Toxoplasma gondii in young healthy blood donors in Northern Iran.

T. gondii is a life-threatening infection in immunocompromised patients which may be transmitted through blood transfusion. The present study aimed to evaluate the seroprevalence and molecular detection of T. gondii infection and the associated risk factors among young healthy blood donors in the central part of Mazandaran province, northern Iran. Blood samples were taken from 500 participants and the serum was separated. All serum samples were tested for the presence of anti-T. gondii antibodies (IgG) and then all positive samples were evaluated for IgM antibodies using commercial ELISA kits. All IgM positive samples and 66 randomly selected IgG positive samples were further tested by PCR of the REP-529 gene. Anti-Toxoplasma antibodies (IgG) avidity test was performed for 142 IgG positive samples which were randomly selected. In the current study, anti-T. gondii antibodies (IgG) and (IgM) were found in 316 (63.2%) and 3 (0.95 %) participants, respectively. Seropositivity rate of Toxoplasma was higher among blood donors living in rural areas (P=0.000) and those with a history of soil and animal contact (P<0.05). PCR of the REP-529 gene showed T. gondii DNA in 21 out of 66 samples. The REP-529 gene was not detected in IgM positive samples. Low avidity antibodies (IgG) was found in 23.2% of the IgG positive samples. In conclusions, this study found that the prevalence of toxoplasmosis among young healthy blood donors in north of Iran was high. To reduce the risk of parasite transmission, leukofilteration method are recommended for donated blood used for immunosuppressed patients.

Seroprevalence and molecular detection of Toxoplasma gondii in young healthy blood donors in Northern Iran

@#T. gondii is a life-threatening infection in immunocompromised patients which may be transmitted through blood transfusion. The present study aimed to evaluate the seroprevalence and molecular detection of T. gondii infection and the associated risk factors among young healthy blood donors in the central part of Mazandaran province, northern Iran. Blood samples were taken from 500 participants and the serum was separated. All serum samples were tested for the presence of anti-T. gondii antibodies (IgG) and then all positive samples were evaluated for IgM antibodies using commercial ELISA kits. All IgM positive samples and 66 randomly selected IgG positive samples were further tested by PCR of the REP-529 gene. Anti-Toxoplasma antibodies (IgG) avidity test was performed for 142 IgG positive samples which were randomly selected. In the current study, anti-T. gondii antibodies (IgG) and (IgM) were found in 316 (63.2%) and 3 (0.95 %) participants, respectively. Seropositivity rate of Toxoplasma was higher among blood donors living in rural areas (P=0.000) and those with a history of soil and animal contact (P<0.05). PCR of the REP-529 gene showed T. gondii DNA in 21 out of 66 samples. The REP-529 gene was not detected in IgM positive samples. Low avidity antibodies (IgG) was found in 23.2% of the IgG positive samples. In conclusions, this study found that the prevalence of toxoplasmosis among young healthy blood donors in north of Iran was high. To reduce the risk of parasite transmission, leukofilteration method are recommended for donated blood used for immunosuppressed patients.

Nanofiber Expansion of Umbilical Cord Blood Hematopoietic Stem Cells.

BACKGROUND: The aim of this study was the ex vivo expansion of Umbilical Cord Blood hematopoietic stem cells on biocompatible nanofiber scaffolds. MATERIALS AND METHODS: CD133+ hematopoietic stem cells were separated from umbilical cord blood using MidiMacs (positive selection) system by means of monocolonal antibody CD133 (microbeads); subsequently, flowcytometry method was done to assess the purity of separated cells. Isolated cells were cultured on plate (2 Dimensional) and fibronectin conjugated polyethersulfon nanofiber scaffold, simultaneously (3 Dimensional). Colony assay test was performed to show colonization ability of expanded cells. RESULTS: Cell count analysis revealed that expansion of hematopoietic stem cells in 2dimensional (2D) environment was greater than 3dimensional (3D) condition (p= 0.01). Assessment of stem cell- phenotype after expansions was performed by flowcytometric analysis which is showed that the maintenance of CD133 marker in expanded cells in 3 dimensional condition were higher than expanded cells in 2 dimensional condition (p=0.01). Moreover, colony assay test was performed before and after of expansion to show colonization ability of expanded cells both in 3D and 2D culture and results revealed more ability of 3D culture compared with 2D culture (p= 0.03). CONCLUSION: The results of current study confirmed that umbilical cord blood CD133+ haematopoietic stem cells are able to expand on fibronectin conjugated polyethersulfon scaffold. These findings indicated that 3D is a proper and valuable cell culture system for hematopoietic stem cells expansion, compared to 2D in invitro situation.

Primary Antibody Deficiency in a Tertiary Referral Hospital: A 30-Year Experiment.

BACKGROUND: Primary antibody deficiency (PAD) is the most common group of primary immunodeficiency disorders (PID), with a broad spectrum of clinical features ranging from severe and recurrent infections to asymptomatic disease. OBJECTIVES: The current study was performed to evaluate and compare demographic and clinical data in the most common types of PAD. MATERIALS AND METHODS: We performed a retrospective review of the medical records of all PAD patients with a confirmed diagnosis of common variable immunodeficiency (CVID), hyper IgM syndrome (HIgM), selective IgA deficiency (SIgAD), and X-linked agammaglobulinemia (XLA) who were diagnosed during the last 30 years at the Children's Medical Center, Tehran, Iran. RESULTS: A total number of 280 cases of PAD (125 CVID, 32 HIgM, 63 SIgAD, and 60 XLA) were enrolled in the study. The median (range) age at the onset of disease in CVID, HIgM, SIgAD, and XLA was 2 (0-46), 0.91 (0-9), 1 (0-26), and 1 (0-10) years, respectively. Gastrointestinal infections were more prevalent in CVID patients, as were central nervous system infections in XLA patients. Autoimmune complications were more prevalent in HIgM patients, malignancies in CVID patients, and allergies in SIgAD patients. The mortality rate for CVID, HIgM, and XLA was 27.2%, 28.1%, and 25%, respectively. No deaths were reported in SIgAD patients. CONCLUSIONS: SIgAD patients had the best prognosis. While all PAD patients should be monitored for infectious complications, special attention should be paid to the finding of malignancy and autoimmune disorders in CVID and HIgM patients, respectively.

Primary antibody deficiency in a tertiary referral hospital: a 30-year experiment

Background: Primary antibody deficiency (PAD) is the most common group of primary immunodeficiency disorders (PID), with a broad spectrum of clinical features ranging from severe and recurrent infections to asymptomatic disease. Objectives: The current study was performed to evaluate and compare demographic and clinical data in the most common types of PAD. Materials and Methods: We performed a retrospective review of the medical records of all PAD patients with a confirmed diagnosis of common variable immunodeficiency (CVID), hyper IgM syndrome (HIgM), selective IgA deficiency (SIgAD), and X-linked agammaglobulinemia (XLA) who were diagnosed during the last 30 years at the Children’s Medical Center, Tehran, Iran. Results: A total number of 280 cases of PAD (125 CVID, 32 HIgM, 63 SIgAD, and 60 XLA) were enrolled in the study. The median (range) age at the onset of disease in CVID, HIgM, SIgAD, and XLA was 2 (0-46), 0.91 (0-9), 1 (0-26), and 1 (0-10) years, respectively. Gastrointestinal infections were more prevalent in CVID patients, as were central nervous system infections in XLA patients. Autoimmune complications were more prevalent in HIgM patients, malignancies in CVID patients, and allergies in SIgAD patients. The mortality rate for CVID, HIgM, and XLA was 27.2%, 28.1%, and 25%, respectively. No deaths were reported in SIgAD patients. Conclusions: SIgAD patients had the best prognosis. While all PAD patients should be monitored for infectious complications, special attention should be paid to the finding of malignancy and autoimmune disorders in CVID and HIgM patients, respectively (AU)

Antecedentes: Las inmunodeficiencias humorales primarias (PAD) es el grupo más frecuente de inmunodeficiencias primarias (IDP), y engloba un amplio espectro de características clínicas, que van desde los pacientes con infecciones graves y recurrentes a los casos asintomáticos. Objetivos: El presente estudio se realizó para evaluar y comparar los datos demográficos y clínicos de los tipos más comunes de PAD. Materiales y Métodos: Se revisaron retrospectivamente, las historias clínicas de todos los pacientes con PAD con un diagnóstico confirmado de: inmunodeficiencia variable común (CVID), síndrome de hiper IgM (HIgM), deficiencia selectiva de IgA (SIgAD),y de agammaglobulinemia ligada al cromosoma X (XLA), que fueron diagnosticados durante los últimos 30 años, en el Centro Médico de Niños, Teherán, Irán. Resultados: Se incluyeron en este estudio un total de 280 casos de PAD, englobando 125 pacientes con CVID, 32 HIgM, 63 SIgAD, y 60 pacientes con XLA. La mediana (rango) de edad al inicio de la enfermedad en la CVID, HIgM, SIgAD y XLA fue: 2 (0-46), 0,91 (0-9), 1 (0-26) y 1 (0-10) años, respectivamente. Las infecciones gastrointestinales fueron más frecuentes en los pacientes con CVID, mientras que las infecciones del sistema nervioso central lo fueron en la XLA. Las complicaciones autoinmunes fueron más prevalentes en los pacientes con HIgM, los tumores malignos en las CVID y las enfermedades alérgicas en las SIgAD. La tasa de mortalidad de CVID, HIgM y XLA fue 27,2%, 28,1% y 25%, respectivamente. No hubo mortalidad en el grupo de pacientes con SIgAD. Conclusiones: Los pacientes con SIgAD tuvieron el mejor pronóstico. Aunque todos los pacientes con PAD deben ser controlados estrechamente para evitar las complicaciones infecciosas, se debe prestar especial atención a la aparición de enfermedades malignas y autoinmunes en los pacientes con CVID y HIgM, respectivamente (AU)

Identification and Characterization of the Antigens Expressed On the Surface of Human Erythrocytes Infected With Plasmodium falciparum.

BACKGROUND: Molecules expressed on the surface of infected erythrocytes (IE) with Plasmodium falciparum play important roles in malaria pathogenesis and immune evasion. Some of these molecules are specific adhesive ligands mediating adhesion of IE to the vascular endothelium. In the current study, the antigens exposed on the surface of IE with different isolates and various binding subpopulations of P. falciparum were studied. METHODS: A pooled hyper immune serum (HIS) from Malawian adults and eluted antibodies from the surface of the homologous and heterologous parasites were used. The parasite surface molecules were analyzed by Immuno-Gold-Silver enhancement (IGSE) and Western blotting. Mini-column cytoadherence method was used to select various parasite-binding subpopulations. RESULTS: Surface antigens of all the isolates were recognized by HIS and high recognition of antigens was observed in all isolates with homologous eluted antibodies. Western blot analysis showed that the eluted antibodies reacted with a small subset of antigens compared with HIS. Three bands, PfEMP-1, were detected in the Triton X- insoluble fraction of the ICAM-1 binding subpopulation. Another interesting band was ∼ 52-55 kDa in various isolates of P. falciparum. This molecule as defined by its low molecular weight, Triton X-100 solubility, surface location and sensitivity to 1 mg/ml trypsin. CONCLUSION: The IE's surface antigens differed in parental population compared with the selected subpopulations. These molecules could induce isolate-specific immunity. Antibodies purified from the surface of IE can be used as specific reagents to investigate parasite-derived proteins expressed on the surface of IE.

Plasmodium falciparum: Adhesion Phenotype of Infected Erythrocytes Using Classical and Mini-Column Cytoadherence Techniques.

BACKGROUND: Cytoadherence of Plasmodium falciparum- infected erythrocytes to host cells is an important trait for parasite survival and has a major role in pathology of malaria disease. Infections with P. falciparum usually consist of several subpopulations of parasites with different adhesive properties. This study aimed to compare relative sizes of various binding subpopulations of different P. falciparum isolates. It also investigated the adhesive phenotype of a laboratory P. falciparum line, A4, using different binding techniques. METHODS: Seven different P. falciparum isolates (ITG, A4, 3D7 and four field isolates) were cultivated to late trophozoite and schizont and then cytoadherence to cell differentiation 36 (CD36), intercellular cell adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule (V-CAM) and E-selectin were examined. The relative binding sizes of parasite subpopulations to human receptors were measured by mini-column cytoadherence method. The adhesion phenotype of P. falciparum-A4 line was evaluated by in vitro static, flow-based and mini-column binding assays. RESULTS: The relative binding size of ITG, A4 and 3D7 clones to a column made with CHO/ICAM-1 was 68%, 54% and 0%, respectively. The relative binding sizes of these lines to CHO/CD36 were 59.7%, 28.7% and 0%, respectively. Different field isolates had variable sizes of respective CD36 and ICAM1-binding subpopulations. A4 line had five different subpopulations each with different binding sizes. CONCLUSION: This study provided further evidence that P. falciparum isolates have different binding subpopulations sizes in an infection. Furthermore, measurement of ICAM-1 or CD36 binding subpopulations may practical to study the cytoadherence phenotypes of P. falciparum field isolates at the molecular level.

Malaria in mazandaran, northern iran: passive case finding during 1997-2012.

BACKGROUND: Malaria is one of the most important parasitic diseases in tropical and temperate regions. The aim of this study was to determine the trend of malaria in Mazandaran Province, northern Iran during 1997-2012. METHODS: This retrospective study was conducted from 1997 to 2012. The population's study was individuals who registered at health centers of Mazandaran Province. Peripheral blood smear were prepared for each case, stained with Giemsa and examined by light microscope. In addition to demographic data, other parameters including Slide Positive Rate (SPR), Annual Parasite Incidence (API) and Annual Blood Examination Rate (ABER) were analyzed. RESULTS: In total, 844 cases of malaria were reported. Plasmodium vivax was predominant species with 821 cases (97.4%). The number of malaria cases increased from 1997 to 2005 and then decreased to 3 cases in 2011. Some cities had not reported any cases during last three years. The highest infection rate, 163(20.07%), was seen in 2001-02. The SPR had the highest value (0.54%) in 2004-05. The maximum API and ABER were observed in 2001-02 and 1997-98. 641(75.9%) of cases were imported from hyperendemic areas such as Afghanistan and South-eastern Iran and 94 (11.1%) malaria patients were recorded as introduced cases. The highest infection rate of malaria (21.3%) was seen in Babolsar. CONCLUSION: Extensive malaria control should be continued to Mazandaran to become malaria-free region and in prevention of re-introduction stage.

Mini-Column for Cytoadherence: A New Method for Measuring the Relative Size of Binding Subpopulations in Plasmodium falciparum Isolates.

BACKGROUND: Cytoadherence of Plasmodium falciparum- infected red blood cells to endothelial cells is an important mechanism for parasite survival and a major trigger for diseases pathology. Here, we describe a new adhesion assay in which different cell types (CHO, CHO/CD36 and CHO/ICAM-1) are attached to Cytodex beads in a mini-column format to measure the relative sizes of various binding subpopulations as a percentage of the total population. METHODS: Relative size of CD36 and ICAM-1-binding subpopulations of erythrocytes infected with P. falciparum were measured by amount of parasitemia before and after passing the infected erythrocytes through a particular column. RESULTS: The mini-column adhesion assay was a suitable method as parasitemia always reduced after passing through a particular column in independent experiments. For example, in a typical experiment using P. falciparum ITG line, 75% of the parasites are retained on a CHO/ICAM-1 while 0% of clone 3D7 is retained. CONCLUSION: This work introduced and validated a method for measuring the relative size of parasite binding subpopulations and the selection of them. Also, the mini-column method is of value for assessments of cytoadherence and can be used as tool for different applications.

Qualitative study on nutritional knowledge of primary-school children and mothers in Tehran.

The nutritional education demands of primary-school children in Tehran were evaluated in a qualitative study, through 20 focus group discussions, 16 for children and 4 for mothers, among 128 children aged 6-11 years and 32 mothers in 8 primary schools in Tehran. Children knew about the advantages of different food groups, including helping digestion, growth and increasing intelligence. They obtained their knowledge mainly from their parents and television, as well as books, teachers and friends. Mothers thought the sources that had most effect on children's nutritional knowledge were television advertisements, parents and classmates. Most of the children claimed that they preferred to learn about nutrition from their parents and television, e.g. children's programmes and advertisements.

Qualitative study on nutritional knowledge of primary-school children and mothers in Tehran

The nutritional education demands of primary-school children in Tehran were evaluated in a qualitative study, through 20 focus group discussions, 16 for children and 4 for mothers, among 128 children aged 6-11 years and 32 mothers in 8 primary schools in Tehran. Children knew about the advantages of different food groups, including helping digestion, growth and increasing intelligence. They obtained their knowledge mainly from their parents and television, as well as books, teachers and friends. Mothers thought the sources that had most effect on children's nutritional knowledge were television advertisements, parents and classmates. Most of the children claimed that they preferred to learn about nutrition from their parents and television, e.g. children's programmes and advertisements

Incidence of aflatoxins in Iran pistachio nuts.

Aflatoxins (AF) are highly toxic and carcinogenic secondary fungal metabolites and have been detected in various food commodities including pistachio nuts. Pistachio nuts were produced in Iran during March 2002-February 2003 analyzed for aflatoxin B1 (AFB1), aflatoxin B2 (AFB2), aflatoxin G1 (AFG1) and aflatoxin G2 (AFG2) using immunoaffinity column and quantitated by HPLC and/or TLC-scanner. In this regard, 3356 pistachio nut samples were collected. After dividing samples to sub-samples, 10,068 AF analyses were done. Among 10,068 samples analyzed, AFB1 was detected in 3699 samples (36.7% of the total) with the mean and median of 5.9 (+/-41.7) ng/g and 0.1 ng/g, respectively. Total AF (AFT) was detected in 2852 samples (28.3% of the total) with the mean and median of 7.3 (+/-53.2)ng/g and 0.4 ng/g, respectively. AFB1 level in 1191 samples (11.8%) was above the maximum tolerated level (MTL) of AFB1 in pistachio nut in Iran (5 ng/g). Regarding AFT, the mean contamination level (7.3 ng/g) was lower than MTL of AFT in pistachio nut in Iran as well as lower than the proposed draft maximum level of Codex Committee on Food Additives and Contaminants for AFT (15 ng/g), and only 7.5% of samples had levels above the MTL.

Prevalence of overweight and obesity in adolescent Tehrani students, 2000-2001: an epidemic health problem.

OBJECTIVE: Overweight has become a public health problem in most developing countries. Evidence suggests that adolescence is a critical period in determining adulthood obesity and its complications. The present study was carried out to assess the prevalence of overweight and obesity among secondary school students. DESIGN AND SETTING: This descriptive study was conducted in Tehran city, 2000-2001. Body weight and height were measured and body mass index (BMI) values were calculated. Underweight, overweight and obesity were defined as <5th, > or = 85th and > or = 95th percentile, respectively, of age- and sex-specific BMI values from the National Center for Health Statistics/Centers for Disease Control and Prevention (2000). SUBJECTS: Using a multistage sampling method, 2321 students (1068 males and 1253 females) aged 11-16 years were assessed in Tehran, the capital city of Iran. RESULTS: The overall prevalences of overweight and obesity were 21.1 and 7.8%, respectively. The prevalence of overweight among girl students (i.e. 23.1%; 95% confidence interval (CI) 20.8-25.4) was significantly higher than that among boys (i.e. 18.8%; 95% CI 16.5-21.1, P=0.01) even after adjustment for age (odds ratio 1.26, 95% CI 1.03-1.55, P=0.02). No significant risk of obesity associated with age was found in girls or boys. In both sexes, median values of age-specific BMI in this study were statistically higher than corresponding values collected in Tehrani adolescents 10 years ago (P=0.03). Similarly, a significant difference was seen between girl students in this study and the reference population (P=0.03). CONCLUSION: According to this study, overweight, especially in girls, should be considered an epidemic health problem among adolescent students in Tehran.