Value of thyroid and rheumatologic studies in the evaluation of peripheral neuropathy

Abstract

SummaryPeripheral neuropathy is a common disorder, often prompting an extensive initial laboratory evaluation. The initial evaluation is particularly challenging to primary care physicians and neurologists because of the broad differential diagnosis. Although screening thyroid and rheumatologic tests are frequently ordered, the diagnostic yield of these tests is unclear. Data from our institution were collected on patient demographics, clinical characteristics including warning signs suggestive of a diagnosis other than distal symmetric polyneuropathy, history of thyroid or rheumatologic disease, and laboratory tests ordered. Thyroid and rheumatologic screening tests are commonly ordered in the evaluation of peripheral neuropathy. Our findings suggest a low aggregate value of these tests based on low yield and infrequent changes in the suspected etiology or management of these patients. P eripheral neuropathy encompasses a heterogeneous group of disorders, including distal symmetric polyneuropathy, multiple mononeuropathies, and demyelinating neuropathies, among many others. Peripheral neuropathy is a prevalent condition affecting approximately 2% of the general population and as many as 8% of those over the age of 55.1,2 Distal symmetric polyneuropathy (DSP) is the most frequently encountered form of peripheral neuropathy, typically presenting symmetrically in the feet with pain, *These authors contributed equally to this work.

Diagnostic value of blood tests for occult causes of initially idiopathic small-fiber polyneuropathy

“…Of note, fewer than half of patients with SS-associated painful neuropathy are SS-seropositive [56], thus the actual prevalence of Sjögren’s syndrome is even higher. However, the 28% prevalence of high ESR here is comparable to the 22.3% prevalence identified in an older, male-predominant Michigan cohort [22]. …”

“…Serologic markers for all 3 conditions were far more often abnormal in the MGH cohort than in the population (Table 2), further evidence linking these conditions to SFPN and suggesting that some cases of iiSFPN are immune mediated. The current study reported the highest prevalence of ANA ≥ 1:160 (27.5%), with other surveys reporting 11% [50], 12.6% [22], and 4.6%. [60].…”

“…Its prevalence here (14.7%) and in all other U.S. neuropathy cohorts (6.1% and 22.7% in Michigan [7, 22], 11% in Ohio [32], 7% and 11% in New York [13, 19]), are all far below the NHANES-based U.S. population prevalences (e.g., 44.9% for adults aged 45–65) [40]. Plus, a prospective Minnesota study that found no increased risk for sensory polyneuropathy among prediabetic patients versus healthy controls also supports the lack of an association [16].…”

“…The 3.9% sample prevalence of monoclonal gammopathy in the population and rates from most other U.S. studies (3.0% in Utah [60], 4.0% in Michigan [22], 7.0% in New York [19]) are slightly higher than the 3.2% prevalence of MGUS in U.S. adults over age 50 even though they include patients under 50 [35]. Although inconclusive, this comparison suggests the need for a targeted study.…”

“…The second largest group of SFPN patients, comprising 20–50% in recent series [19, 22, 26, 51, 69], is those with “initially idiopathic” or cryptogenic causes (here abbreviated as iiSFPN). They are the focus of the current study.…”