Toyota Process Redesign in Reducing Thyroid Gland FNA Error
Toyota Process Redesign in Reducing Thyroid Gland FNA Error
Our objective was to determine whether the Toyota Production System process redesign resulted in diagnostic error reduction for patients who underwent cytologic evaluation of thyroid nodules. In this longitudinal, nonconcurrent cohort study, we compared the diagnostic error frequency of a thyroid aspiration service before and after implementation of error reduction initiatives consisting of adoption of a standardized diagnostic terminology scheme and an immediate interpretation service. A total of 2,424 patients underwent aspiration. Following terminology standardization, the false-negative rate decreased from 41.8% to 19.1% (P = .006), the specimen nondiagnostic rate increased from 5.8% to 19.8% (P < .001), and the sensitivity increased from 70.2% to 90.6% (P < .001). Cases with an immediate interpretation had a lower noninterpretable specimen rate than those without immediate interpretation (P < .001). Toyota process change led to significantly fewer diagnostic errors for patients who underwent thyroid fine-needle aspiration.
Gharib and Castro and Gharib estimated that 300,000 new thyroid gland nodules are detected yearly in the United States, and Solomon estimated that at least 288,000 patients per year undergo thyroid gland fine-needle aspiration (FNA). Assuming a false-negative rate of 5%, a false-positive rate of 3%, a follicular neoplasm diagnostic rate of 11%, and a nonneoplastic follow-up rate of 20% for patients with a follicular neoplasm, 15,000 patients per year with nonneoplastic disease have surgery and 14,400 patients with neoplastic disease have delays in surgery.
In practice, the variability in thyroid gland FNA diagnostic accuracy is wide and most likely contributes to regional and institutional differences in patient treatment and outcomes. The literature is replete with studies documenting causes of thyroid gland FNA error, but data are lacking on process improvement studies and determining the successes and failures of attempted error reduction. The national targeting of diagnostic testing from a patient safety viewpoint has lagged behind other quality improvement efforts.
Effective process redesign of diagnostic testing practice entails altering the clinical and pathology domains, and several methods of process redesign are being tested in health care. The Toyota Production System method aptly applies to diagnostic testing because it focuses on product (ie, specimen and diagnosis) quality and the steps involved in testing are similar to the steps involved in manufacturing. Raab et al and Nodit et al reported that the major cause of diagnostic error, including thyroid gland FNA error, was the interpretation of less than optimal samples, leading to false-negative and false-positive diagnoses. Raab et al showed that adoption of Toyota principles in Papanicolaou testing pathway redesign led to improved Papanicolaou test quality and fewer diagnostic errors.
In the present study, we examined thyroid gland FNA error and quality from a Toyota perspective, and we changed specific processes based on error reduction initiatives drawn from the literature and our own root cause analysis. The initiatives consisted of the following: (1) creating an immediate FNA interpretation service and (2) standardizing FNA diagnostic terminology. We hypothesized that the implementation of these initiatives would result in improvement of specimen quality and fewer diagnostic errors. We tested these hypotheses by comparing the thyroid gland FNA specimen adequacy and diagnostic accuracy rates for prestandardized and poststandardized terminology cohorts and immediate and nonimmediate FNA interpretation cohorts.
Abstract and Introduction
Abstract
Our objective was to determine whether the Toyota Production System process redesign resulted in diagnostic error reduction for patients who underwent cytologic evaluation of thyroid nodules. In this longitudinal, nonconcurrent cohort study, we compared the diagnostic error frequency of a thyroid aspiration service before and after implementation of error reduction initiatives consisting of adoption of a standardized diagnostic terminology scheme and an immediate interpretation service. A total of 2,424 patients underwent aspiration. Following terminology standardization, the false-negative rate decreased from 41.8% to 19.1% (P = .006), the specimen nondiagnostic rate increased from 5.8% to 19.8% (P < .001), and the sensitivity increased from 70.2% to 90.6% (P < .001). Cases with an immediate interpretation had a lower noninterpretable specimen rate than those without immediate interpretation (P < .001). Toyota process change led to significantly fewer diagnostic errors for patients who underwent thyroid fine-needle aspiration.
Introduction
Gharib and Castro and Gharib estimated that 300,000 new thyroid gland nodules are detected yearly in the United States, and Solomon estimated that at least 288,000 patients per year undergo thyroid gland fine-needle aspiration (FNA). Assuming a false-negative rate of 5%, a false-positive rate of 3%, a follicular neoplasm diagnostic rate of 11%, and a nonneoplastic follow-up rate of 20% for patients with a follicular neoplasm, 15,000 patients per year with nonneoplastic disease have surgery and 14,400 patients with neoplastic disease have delays in surgery.
In practice, the variability in thyroid gland FNA diagnostic accuracy is wide and most likely contributes to regional and institutional differences in patient treatment and outcomes. The literature is replete with studies documenting causes of thyroid gland FNA error, but data are lacking on process improvement studies and determining the successes and failures of attempted error reduction. The national targeting of diagnostic testing from a patient safety viewpoint has lagged behind other quality improvement efforts.
Effective process redesign of diagnostic testing practice entails altering the clinical and pathology domains, and several methods of process redesign are being tested in health care. The Toyota Production System method aptly applies to diagnostic testing because it focuses on product (ie, specimen and diagnosis) quality and the steps involved in testing are similar to the steps involved in manufacturing. Raab et al and Nodit et al reported that the major cause of diagnostic error, including thyroid gland FNA error, was the interpretation of less than optimal samples, leading to false-negative and false-positive diagnoses. Raab et al showed that adoption of Toyota principles in Papanicolaou testing pathway redesign led to improved Papanicolaou test quality and fewer diagnostic errors.
In the present study, we examined thyroid gland FNA error and quality from a Toyota perspective, and we changed specific processes based on error reduction initiatives drawn from the literature and our own root cause analysis. The initiatives consisted of the following: (1) creating an immediate FNA interpretation service and (2) standardizing FNA diagnostic terminology. We hypothesized that the implementation of these initiatives would result in improvement of specimen quality and fewer diagnostic errors. We tested these hypotheses by comparing the thyroid gland FNA specimen adequacy and diagnostic accuracy rates for prestandardized and poststandardized terminology cohorts and immediate and nonimmediate FNA interpretation cohorts.
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