Nonaspiration Biopsy, Small Needles Improve Thyroid Nodule Diagnosis

Nancy A. Melville

August 06, 2018

Use of the capillary action technique (nonaspiration) in fine-needle biopsy of routine thyroid nodules significantly reduces rates of nondiagnostic cytopathology compared  with aspiration, and the use of smaller needles in the biopsies furthermore does not compromise the rates of diagnostic success compared with larger needles, according to results of a new meta-analysis on the issue.

"Given the statistically significant deceased rate of non-diagnostic cytopathology with capillary action and the potential for increased pain and complications with larger needles without a proven benefit, needle biopsy of routine thyroid nodules should be performed without aspiration and with smaller needle gauges," the authors conclude.

International consensus on the use of fine-needle biopsy in the evaluation of thyroid nodules is strong, but there is less agreement on which of the various techniques provide the best chances of diagnostic success.

The key options include fine-needle aspiration, in which negative pressure from the syringe and the shearing of the needle allow for the collection of tissue, or nonaspiration needle biopsy, also called the capillary action technique, in which thyroid tissue is passively drawn into the needle hollow with hydrostatic pressure.

There is also no consensus about the optimal needle gauge to use: Larger needle gauges may provide more tissue volume than smaller-gauge needles, but there is debate on the issue.

Larger Needles: More Pain, More Complications, and No Clear Benefit

To compare the evidence on these differing options, William J. Moss, MD, and colleagues from the Department of Surgery and Division of Otolaryngology—Head and Neck Surgery, University of California, San Diego, conducted the systematic review of 24 articles with a collective 4428 nodules requiring evaluation. The report was published in the July issue of Thyroid.

Of the articles, 20 compared capillary action (nonaspiration) to aspiration, and 6 evaluated needle gauge. Most of the trials were blinded, with or without randomization, and all but 2 were prospective.

A random-effects model analysis showed the capillary action method to be associated with a significantly greater reduction in the relative risk of having nondiagnostic cytopathology (relative risk, 0.57; P = .02).

Meanwhile, there was a trend, though not statistically significant, of smaller-gauge needles (25- to 27-gauge) showing more favorable outcomes, suggesting no apparent improvement in benefits with the larger needles that are associated with more pain.

In addition to being more painful, large-needle biopsies may also have more complications, which, though rare, can include infections, vocal cord paralysis, and hematomas, the authors say.

Senior author Moss said the lack of a diagnostic benefit with the larger-gauge needles is not surprising.

"A wider bore doesn't necessarily mean more tissue, particularly if the capillary action method is used," he told Medscape Medical News.

"Also, blood makes interpreting thyroid histopathology more difficult [as] larger needles mean more blood."

The potential for blood contamination with larger needles is particularly notable with thyroid nodules as opposed to other biopsies because of the vascular nature of thyroid gland tissue, he pointed out.

Better Technology Will Yield Better Results

The analysis has several notable limitations, the authors acknowledge, including the fact that only 8 of the 24 studies confirmed the use of ultrasound guidance for all biopsies, representing a possible confounder as the lack of consistent ultrasound use could result in increased nondiagnostic attempts.

And with thyroid nodules in general being highly diverse with a "myriad of anatomic features," certain subtypes may indeed be more appropriately sampled with aspiration or larger needles, they say.

For example, some studies did show that "for nodules with multiple ND [nondiagnostic] biopsies, larger diameter or core needles may be advantageous," they concede.

As technology advances, diagnosis should improve, they add, noting,

"There are a variety of negative pressure devices and modified needles that have shown promise as adjunct technologies in needle biopsy of the thyroid."

With millions of thyroid needle biopsies performed each year around the world, the problem of nondiagnostic samples, classified as Bethesda I, is persistent.

The use of ultrasound guidance, common in the United States, improves outcomes, but even with the guidance, an estimated 10% of nodule assessments are nondiagnostic, with some studies suggesting much higher rates, the authors say.

Moss concluded that the take-home message from the collective evidence is that "when performing an initial biopsy of a standard thyroid nodule, 25 to 27 gauge needles should be used, along with a non-aspiration or 'capillary action' technique."

Moss has disclosed no relevant financial relationships.

Thyroid. 2018;7:857-863. Full text

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