Thyroid survey by the Ministry of the Environment was conducted in order to find out the incidence of thyroid nodules and cysts in children in areas not affected by radiation contamination due to the Fukushima nuclear accident. The official name for the survey is “Study of presence of thyroid findings in three prefectures outside Fukushima Prefecture.” It will be referred to as the “MOE thyroid survey” hereafter.
A preliminary result for the MOE thyroid survey was presented at a press conference on March 8, 2013, which revealed a higher percentage of A2 and B assessments than Fukushima Prefecture, at 56.6% and 1.0% respectively. (In Fukushima Prefecture, the cumulative results for A2 and B assessments were 41.8% and 0.6%, respectively). The A2 assessment includes nodules 5.0 mm or smaller or cysts 20.0 mm or smaller, only requiring observation and a follow-up ultrasound in two years. The B assessment includes nodules 5.1 mm or larger and cysts 20.1 mm or larger, requiring a secondary examination including a more detailed ultrasound examination, blood test and a possible fine-needle aspiration biopsy. As of mid-February, it was reported that the result of the MOE thyroid survey was going to be available by the end of March, which is the end of this fiscal year. It was unclear why a preliminary result was reported at this time.
Study of presence of thyroid findings in three prefectures outside Fukushima Prefecture (MOE thyroid survey) A = 56.6%; B = 1.0%
Fukushima Prefecture survey
Cumulative ratio of assessment A = 41.8%; B = 0.6%.
The comparison of the two surveys was quickly publicized as a proof that the thyroid abnormalities discovered in Fukushima are not likely due to the effect of radiation, as a higher percentage of abnormalities were found outside Fukushima Prefecture.
Shinichi Suzuki of Fukushima Medical University, a physician who is in charge of the thyroid examination in Fukushima, had maintained that the “high” percentage of thyroid ultrasound abnormalities in Fukushima children was because of a high sensitivity of the ultrasound equipment being used. Since there was no comparable study available in terms of mass screenings of children using thyroid ultrasound, the Japanese government decided to launch a study outside Fukushima Prefecture.
This MOE three-prefecture survey was commissioned to the Japan Association of Breast and Thyroid Sonology (JABTS), http://www.jabts.net/, on August 31, 2012, which won an open competitive bidding. At the time, it was supposed to be a control study to obtain data to compare to the Fukushima result. However, it was allegedly explained at the press conference for the preliminary result that this study was not considered a control study but rather a study to compare incidence amongst the three prefectures. This is quite strange, since they reported the total incidence of the three prefectures.
The purpose of the survey was said to relieve the anxiety of Fukushima parents who were worried about their children’s A2 assessments. Did it really accomplish that?
Unlike the Fukushima survey, the MOE thyroid survey apparently does not include children younger than 3. Also, the survey population appears to be from a fixed location such as a particular school, which might not be a general representation of the population.
The higher percentages of 56.6% and 1.0% did not come with detailed information such as the proportion of nodules vs. cysts or the size and age distributions of nodules and cysts. It is possible that there were many findings of cysts smaller than 3.0 mm, which are not considered clinically significant yet included in the A2 assessment. Moreover, the percentage of the B assessment, eligible for the secondary examination, does not mean as much as the result of the secondary examination. For instance, in fiscal year H23, 186 out of 38,114 had B assessment, 162 underwent the secondary examination, and 76 of 162 had fine-needle aspiration biopsy. Ten children were suspected of having thyroid cancer. Three of them were confirmed to have thyroid cancer and already had surgery. Seven others will undergo surgery for tissue biopsy for confirmation.
Incidentally, Japan Association of Breast and Thyroid Sonology was one of the seven organizations included in the "Diagnostic Criteria Inquiry Subcommittee of Thyroid Examination Advisory Committee." This committee decided on diagnostic criteria for thyroid ultrasound examination for the Fukushima Prefecture Health Management Survey. However,
no record could be found, at least on the Internet, regarding minutes of proceedings of this Subcommittee, revealing a potential lack of transparency.
Moreover, one of the board members of the Japan Association of Breast and Thyroid Sonology happens to be Shinichi Suzuki, who is in charge of the Fukushima thyroid examination. This could compromise the neutrality and objectivity of the MOE thyroid survey.
It is difficult to find radiation-free areas in Japan due to the nationwide incineration of disaster debris with some radiation contamination as well as the widespread distribution of contaminated foodstuff. Also, Kofu-city, Yamanashi, did get some Fukushima fallout. Rather than being content that Fukushima’s thyroid abnormalities are not much different from those other prefectures, there might be a bigger issue of why there are such high percentages of abnormalities found in children all over Japan.
We will await the full report by the Ministry of the Environment on this “comparative” study.