開発した手根管症候群の簡易的スクリーニング・ツールを用いて精密機械工場の
従業員 1,500人を対象として手根管症候群患者を発見できるかどうかを調査した．第
1 次調査における回答者 1,103 人のうち，手に何らかの自覚症状を有する人は 104 人（9.4%）であった．その中で面接・検査を希望した 28人に対して第 2次調査（知覚 検査，症状誘発テスト，NCSなど）を実施し，病院受診をしていなかった 6人 11手が 手根管症候群と診断された．また，面談･検査を実施した 28人を対象として 7点をカ ットオフ値としたスクリーニング･ツールの感度は66.7%，特異度は36.4%であった．
開発したスクリーニング・ツールの有効性と研究の限界
本研究の背景には，手根管症候群患者の早期診断・早期治療を実現させることに よって個人の生活の質（以下，QOL）を改善させようという大目標があった．フィールド 調査によって実際に手根管症候群患者の発見ができたことは，開発したスクリーニン グ・ツールが有効であったことを示している．また，本スクリーニング･ツールは質問紙 であることから低コスト・低リスクであり，現実的実現可能性が極めて高いといえる．し かし，本質問表において陽性を示すカットオフ値 7 点以上であっても頸椎疾患や他 の神経疾患の疑いを有するものが多かったことは課題である．そのため今後は，他疾 患との鑑別について質問票の得点パターンの比較に加え，年齢や性別などの要因 を含めて検討していく必要がある．反面，頸椎疾患などに罹患している患者を発見で きたことは，上肢神経疾患のスクリーニング・ツールとして幅広く利用できる可能性を 示唆しているのかも知れない．
一方，手根管症候群の早期診断・早期治療のためには実際の受療行動に結びつ かなければ患者にとって利益があるとはいえない．今回の調査でも第 2 次調査を希 望するものは 30％に満たなかった．そのため自覚症状をもつ人々の受療行動を，い かに変化させるかが，今後の大きな課題である．
謝 辞
本研究を実施するにあたり，ご理解とご協力を頂きました全ての対象者の皆様に 深く感謝申し上げます．また，弘前大学大学院保健学研究科健康支援科学領域老 年保健学分野の對馬 均教授におかれましては，研究および論文作成について多大 なるご指導を賜ったことは勿論ですが，公私に渡って暖かいご助言と励ましのお言葉 を頂いたことに深く感謝申し上げます．
また，カットオフ値を決める研究においてデータ収集にご協力頂きました弘前市の 地域の方々と弘前医療福祉大学の教職員の皆様，フィールド調査の実施について ご快諾とご協力を頂きました弘前航空電子ならびに関連企業を含めた全従業員の 方々に深謝申し上げます．
なお，本研究の一部は，JSPS 科研費 60621109 の助成を受けて実施したもので す．
引用文献
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Abstruct
Development of a Screening Tool Allowing Efficient Early Detection of Carpal Tunnel Syndrome
Akihiro SATO
Department of Development and Aging,
Hirosaki University Graduate School of Health Sciences.
According to large-scale epidemiological studies in Western countries, carpal tunnel syndrome (CTS) has a prevalence of 2-4%, developing in about 3.5 out of 1,000 people each year. Neither the prevalence nor the incidence of CTS in Japan is known. If its prevalence and incidence in Japan are assumed to be comparable to those in Western countries, we can reasonably estimate that there are more than 2.4 million patients with CTS in Japan, with the disease developing in about 420,000 individuals annually.
Although CTS is clearly a disease with a high prevalence, there are no established standard criteria for its diagnosis. In recent years, attempts have been made to establish methods of diagnosing CTS, aimed at facilitating early diagnosis and early treatment of this disease, making use of nerve conduction studies (NCS), induction of symptoms with exogenous stress, and so on.
As a result of these attempts, early diagnosis of CTS is now possible, and high efficacy of treatment can now be expected when dealing with CTS patients. Meanwhile, patients with CTS tend to consult a medical facility only after the disease has become severe.
There thus appears to be a need to resolve the problematic, i.e. delayed, treatment-seeking behavior of patients with this disease. To resolve this problem, it would appear to be important to spread the use of a CTS screening tool which enables a simple self-check to be conducted. In the past, various methods such as hand diagrams,
NCS and ultrasound were attempted in the effort to develop a CTS screening tool. These methods have both advantages and shortcomings, and there is still no screening tool enabling self-checks to be carried out.
Given the above circumstances, we focused on the Carpal Tunnel Syndrome Instrument (CTSI) used globally as an outcome scale in the evaluation of responses to CTS treatment and attempted to develop a unique questionnaire-based self-check type screening tool by modifying the JSSH (Japanese Society for Surgery of the Hand) version of the CTSI (CTSI-JSSH).
Chapter 1 pertains to our study aimed at selecting items for the questionnaire. Because the CTSI-JSSH consists of 19 items, i.e., 11 items related to “symptom severity scale”
and 8 items related to “functional status scale,” we first attempted to reduce the number of items for the purpose of reducing the patient burden. When reducing the number of items, we identified factors related to “symptom severity scale” and “functional status scale” scores and endeavored to select items involving such factors for the new questionnaire. Multiple logistic regression analysis of 100 patients with CTS was carried out, allowing identification of factors related to “functional status scale” scores. Gender (odds ratio 5.22) and abductor pollicis brevis muscle CMAP amplitude (odds ratio 0.80) were thereby identified as important factors. Then, to select actions serving as indicators of CTS-associated dysfunction, the rank correlations of these two factors (gender and CMAP amplitude) to the 8 sub-items of the “functional status scale” were analyzed. This analysis revealed a significant correlation with “fastening a button (rs = -0.30)” in males and with “fastening a button (rs = -0.46),” “unsealing a bottle (rs = -0.30),” “holding a telephone receiver (rs = -0.24)” and “housework (rs = -0.22)” in females. Regarding
“symptom severity scale”, relevant factors were explored employing multiple regression analysis of data from 114 patients with CTS, and the presence/absence of numbness and nocturnal pain were identified as factors influencing this parameter.
On the basis of these results, two items of the “functional status scale” were selected for the new questionnaire, i.e., “fastening a button” (an item showing a significant
correlation in both males and females) and “unsealing a bottle” (the item with the second highest correlation coefficient in females). From the 11 “symptom severity scale” items, three (presence/absence of numbness, presence/absence of nocturnal pain, and premature waking due to nocturnal pain) were selected for the new questionnaire.
Chapter 2 pertains to the study aimed at preparing a questionnaire comprised of 5 items as a CTS screening tool on the basis of the results of the Chapter 1 study and at setting the total score cut-off level to serve as a criterion for judgment. The questionnaire prepared consisted of 5 items, i.e., “presence/absence of symptoms,” “presence/absence of nocturnal pain,” “premature waking due to nocturnal pain, “unsealing a bottle” and
“fastening a button.” Each item was rated on a 1-5 scoring scale (full total score: 25).
Higher scores indicate more intense subjective symptoms. Using this questionnaire, a survey was conducted, involving 32 patients with CTS and the control group consisting of 60 individuals matched to the CTS group for age, gender, height and body weight. On the basis of the total scores in the questionnaire survey, the cut-off level was explored using the ROC curve and Youden’s index. A score of 7 was identified as the optimal cut-off level for distinguishing between the CTS group and the CTS-free group. When the cut-off level was set at a score of 7, sensitivity was 96.9%, specificity was 86.7%, the positive likelihood ratio was 7.27, the negative likelihood ratio was 0.04, the positive predictive value was 79.5%, the negative predictive value was 98.1% and accuracy was 90.2%. These values were comparable to or higher than those obtained by prior studies employing hand diagrams, NCS and ultrasound as screening tools.
Chapter 3 pertains to the field survey conducted to examine the extent to which this tool would allow CTS screening. The survey was conducted with the cooperation of JAE Hirosaki Ltd. (a company producing precision electronic parts, located in Hirosaki City, Aomori Prefecture), adopting its factory as the field testing site and involving 1,500 employees of the company’s production department and affiliated companies. The first survey was conducted by asking all subjects to fill out the questionnaire. Responses were collected from 1,103 subjects who took the first survey (response rate: 73.5%).