2006 Rep. of Turkmenistan: Assessment of virtual IDD elimination in Turkmenistan as a Result of an Effective USI Program
Iodine Deficiency Disorders (IDD) pose a serious threat to health and development of population in many countries of the world. Universal salt iodization (USI) is the most cost-effective, safe and reliable method of iodine prevention, meaning that more than 90% of population should use adequately iodized salt.
IDD elimination program in Turkmenistan started from the early 1990-s. First modern epidemiological assessment was conducted in 1994 and showed existence of iodine deficiency among the population. Goiter prevalence in Ashgabat was 20% and in Dashgowuz – 64%. Based on these results, president’s decree on USI was adopted in Turkmenistan.
In January-March 2004 a national epidemiological representative 30 cluster, school-based survey of 879 schoolchildren aged 8-10 was carried out covering all administrative districts of the country (velajat). The survey was performed based on UNICEF. WHO, ICCIDD guidelines: “Assessment of iodine deficiency disorders and monitoring their elimination” (2001). Results of this survey confirmed adequate level of iodine nutrition of Turkmenistan population on the entire territory of the country. This was achieved by universal availability of quality iodized salt that was found in 100% of the surveyed households. Median
urinary iodine level (170 mcg/l) for the national sample was in the safe range (100-300 mcg/l) recommended by WHO, UNICEF and ICCIDD, and proportion of samples with iodine levels below 100 and 50 mcg/l were significantly below recommended thresholds. Based on results of this survey in 2004 Turkmenistan was proclaimed by UNICEF, WHO and ICCIDD as the country that eliminated iodine deficiency.
However, the 2004 survey did not include assessment of most common clinical feature of iodine deficiency – prevalence of goiter among schoolchildren and pregnant women. Goiter prevalence reflects not only level of iodine nutrition but overall efficiency of IDD elimination program. In situation of adequate iodine nutrition goiter prevalence in children should be below 5%. At the same time, decrease of goiter prevalence in the course of IDD elimination program is rather slow process and goiter prevalence could be still elevated even in situation of normal iodine supply.
The objective of 2006 assessment was to provide data in support of IDD elimination in Turkmenistan as results of effective USI program in place for more than 7 years. Another objective was to pilot more effective and less costly sentinel method for site selection for monitoring of IDD control program through USI.
The Sentinel Study was conducted by research team of Research and Clinical Center for Mother and Child Health Protection (RCC MCHP) with UNICEF support in Akhal, Balkan, Mary velayats and Ashgabat City in September 2006. Sites for the assessment were randomly selected among clusters (schoola) pre-selected for 2004 survey. School children aged 8-10 years and pregnant women (living in the same towns or villages as schoolchildren) were assessed in local health centers.
Totally 253 persons were surveyed: 126 schoolchildren and 117 pregnant women, residing both in urban and rural settings.
Goiter prevalence was assessed by thyroid ulstrasonography (US) using portable US scanner Philips SDR 1200 with 5.0 mHz transducer. Thyroid volume was calculated by Brunn et al. (1993) formula. Reference thyroid volumes (P97) recommended by F.Delange et al (1997) were used for calculation of goiter rate. For adult pregnant women 18 ml was used as a cut-off for normal thyroid volume. All thyroid studies were conducted by UNICEF consultant, Prof. G.Gerasimov (Russia).
Iodine was assayed in spot urine samples using method described by J.Dunn et al. (1993) after wet digestion with ammonium persulfate. Spectrophotometric manual method had the following analytical parameters: – threshold of sensitivity - 5 mcg/l, accuracy – coefficient of variation, CV – 13.6%, analytical recovery – 80 – 104%. For the purpose of internal quality control pooled urine sample with mean concentration 148 mcg/l was used for each batch of analytical analysis. Salt samples were tested directly in field for iodine content using spot express kits. All salt samples were subsequently assayed for
iodine quantity by titration in the laboratory of Sanitary Epidemiological Inspection.
For external quality control of urinary iodine (UI) assays 30% of urinary samples were also tested for UI content in the reference laboratory based in the Endocrinology Research Center (Moscow, Russia). This laboratory stands among most qualified reference laboratories within the Network of Reference Urinary Iodine Laboratories that is supervised by Centers for Disease Control and Prevention (CDC, Atlanta, USA).
Results of external evaluation showed that the Turkmenistan lab has a very high bias with little to no correlation to the Moscow laboratory results. This reflects rather low quality of UI assays. More detailed opinion of CDC experts is presented in Annex 2.
Findings and Conclusions:
Results of the survey conducted in selected sentinel sites in 3 provinces and capital city of Turkmenistan confirm adequate and sustained level of iodine nutrition and elimination of iodine deficiency in this county. Almost 100% of all salt on household level is iodized. Results of urinary iodine assessment (both by laboratory of the Research and Clinical Center for Mother and Child Health Protection and reference laboratory in Russia) show adequate level of iodine supply to population. After almost 8 years of universal salt iodization, this prevention program led to virtual elimination of iodine deficiency disorders. Results of ultrasonography evaluation of thyroid glands in schoolchildren and pregnant women showed only sporadic (2.4%) prevalence of thyroid enlargement (goiter). This is direct evidence that endemic goiter in
Turkmenistan has been virtually eliminated. Assessment of sentinel sites piloted in this survey showed reliability and validity of such approach. In future, it is recommended to conduct similar assessment of urinary iodine and iodine in salt at the same sites on the annual basis.
Urgent measures should be taken to improve quality of iodine assessment in the laboratory of the Research and Clinical Center for Mother and Child Health Protection. For this, senior laboratory analyst should attend training on urinary iodine determination in Tashkent in April, 2007 and, if needed, also get additional training in reference iodine laboratories in Almaty or in Moscow. Turkmenistan laboratory should also join EQUIP program provided by CDC to check quality of UI assessment on a regular basis. To improve quality of iodine assays in salt by laboratories of the Sanitary Epidemiological Inspections, external quality control study should be conducted with support of qualified laboratory in some neighboring country. UNICEF Office could provide necessary assistance to such external control. After introduction of measures
for the improvement of laboratory methods of iodine testing in salt and urine, new round of sentinel studies should be conducted in the second part of 2007 to get updated results on level of iodine nutrition in Turkmenistan.
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