Decision analysis of discordant thyroid nodule biopsy guideline criteria

Abstract

Context: Recently published guidelines are discordant regarding diagnostic approaches to small (10-14 mm) thyroid nodules.

Objective: The objective of the study was to explore the relative desirability of alternative diagnostic approaches to small thyroid nodules using decision analysis.

Design: Four diagnostic approaches to a 10- to 14-mm thyroid nodule are modeled: 1) observation only, consistent with American Thyroid Association guidelines; 2) routine fine-needle aspiration biopsy (FNAB), an approach traditionally chosen by many endocrinologists and consistent with American Thyroid Association guidelines; 3) FNAB only when microcalcifications are present, as recommended by Society of Radiologists in Ultrasound guidelines; and 4) FNAB only when the nodule is hypoechoic and has at least one other ultrasonographic risk factor, as endorsed by American Association of Clinical Endocrinologists guidelines.

Main outcome measures: Measures included expected values; a priori likelihoods of prespecified outcomes; and two-way sensitivity analyses based on the utility of observation only in the setting of thyroid cancer and thyroid surgery for benign, asymptomatic thyroid disease.

Results: Expected values (EVs) were similar among decision alternatives modeling Society of Radiologists in Ultrasound guidelines, American Association of Clinical Endocrinologists guidelines, and routine observation (EVs from 0.912 to 0.927). Routine FNAB had the lowest EV (0.757-0.861), primarily related to a high a priori likelihood of having surgery for a benign nodule.

Conclusions: As a general approach to 10- to 14-mm thyroid nodules, routine FNAB appears to be the least desirable. This analysis offers additional data that physicians can use when choosing diagnostic approaches to small thyroid nodules based on perceived risks of delayed cancer diagnosis and unnecessary thyroid surgery.

Figure 1

Decision analysis model. P(cancer), Probability of cancer; observation_cancer, utility of observation alone in the setting of thyroid cancer; P(inad_FNAB), probability of repeatedly inadequate FNABs; surgery_benign, utility of surgery for a benign nodule; P(indet_FNAB), probability of indeterminate FNAB; P(hyperfunction), probability that a nodule with an indeterminate FNAB result will be hyperfunctioning on I-123 scintigraphy; P(indet_cancer), probability that a nodule with indeterminate FNAB (and not hyperfunctioning on I-123 scintigraphy) will be cancer; P(pos_FNAB), probability of positive (malignant) FNAB reading; TP, true positive; PPV(FNAB), PPV of FNAB; FP, false positive; NPV(FNAB), NPV of FNAB; FN, false negative; TN, true negative; mCa, microcalcifications; P(pos_mCa), probability of observing mCa on US; PPV(mCa), PPV of mCa; NPV(mCa), NPV of mCa; P(pos_FNAB_mCa), probability of positive (malignant) FNAB reading when mCa are present; PPV(FNAB_mCa), PPV of FNAB when mCa are present; NPV(FNAB_mCa), NPV of FNAB when mCa are present; hypo-plus, hypoechoic plus at least one other US risk factor; P(pos_hypo-plus), probability of observing hypo-plus on US; PPV(hypo-plus), PPV of hypo-plus; NPV(hypo-plus), NPV of hypo-plus; P(pos_FNAB_hypo-plus), probability of positive (malignant) FNAB reading when hypo-plus present; PPV(FNAB_hypo-plus), PPV of FNAB when hypo-plus present; NPV(FNAB_hypo-plus), NPV of FNAB when hypo-plus present.

Figure 2

Two-way sensitivity analysis: utility of observation in the setting of thyroid cancer (observation_cancer) vs. utility of surgery for a benign nodule (surgery_benign). Conservative FNAB parameter estimates (FNAB assumptions A) were 95% FNAB sensitivity and specificity; 10% likelihood of persistently inadequate FNAB; and 15% likelihood of indeterminate FNAB. Optimistic FNAB parameter estimates (FNAB assumptions B) were 98% FNAB sensitivity and specificity; 5% likelihood of persistently inadequate FNAB; and 10% likelihood of indeterminate FNAB. US, FNAB based on ultrasound findings as recommended by AACE or SRU.