To the Editors:
Walker-Bone et al (1) have provided the largest available study on the prevalence and impact of musculoskeletal disorders of the upper limb in the general population. However, their claim that the reported estimates of prevalence for the specific disorders, as assessed by the Southampton examination protocol, are generally similar to those available in the literature is scarcely plausible for carpal tunnel syndrome (CTS). CTS is thought to be the most common nerve-entrapment syndrome and has been used as an illustrative example of repetitive strain injuries as a whole (2). Yet the reported prevalence of CTS—1.2% in men and as little as 0.9% in women—was lower than that of almost all other musculoskeletal disorders of the upper limb under examination (among women, even de Quervain's disease turned out to be more frequent) (1), and this surely requires some discussion.
The authors stated that their clinically based diagnosis of CTS was consistent with case definitions used in the field of epidemiology, citing general population prevalence studies by Atroshi et al (3) and De Krom et al (4). The frequency of CTS is known to be higher in women than in men. Atroshi et al (3) estimated a prevalence of “clinically certain CTS” of 4.6% in women, while De Krom et al (4) concluded that CTS was “a common disorder in women” (3.4% already diagnosed, plus 5.8% undetected). In 2 British towns, women had an ∼2-fold higher average annual incidence of neurophysiologically confirmed CTS (5). Based on codified hospital discharge records (for 1997–2000) from the Emilia-Romagna region of Italy (population 3.98 million), we found that almost 6,000 inhabitants were hospitalized each year because of CTS (receiving surgical treatment in 96% of cases). Using the Standard European Population, we can estimate a standardized inpatient incidence of 176.69 per 100,000 (95% confidence interval 176.67–176.71) for women and 42.49 (42.48–42.50) for men (suggesting a likely overall prevalence of surgically treated cases of 2% or more in the general population).
The Southampton examination protocol is a highly relevant initiative. Its repeatability has been well validated (6, 7), but the diagnostic concordance of their CTS classification criteria does not appear to have been systematically tested. We suspect that the apparent rarity of CTS in women (with respect to, for example, de Quervain's disease) may be connected with the high prevalence of cases classified as “nonspecific wrist/hand pain” (8.7% in men, 11.5% in women). We also have reservations regarding the appropriateness of considering only patients who were symptomatic “in the last 7 days” (1, 7) for a chronic musculoskeletal disorder that often displays intermittent symptoms (8) (and is thought to have a hormonal component in women). Based on the evidence from the important study by Walker-Bone et al (1), we think that the Southampton protocol's classification criteria for CTS require further consideration to avoid the risk of underestimating the frequency of CTS.