Diagnosing Sjögrens Syndrome
The diagnosis of SS remains problematic. Complaints of dry eyes and dry mouth are both common and nonspecific. Against this background, seven separate sets of diagnostic criteria have been proposed for SS during the past 35 years, distinguished primarily by the weight given to the different clinical and laboratory manifestations of the disease. The more stringent San Diego criteria for the diagnosis of SS were proposed in 1986. The most recent classification criteria for SS, proposed by investigators in the European Economic Community (EEC), are a less stringent compromise. However, proponents of the San Diego criteria argue that only 15% of the patients diagnosed with SS by the EEC criteria fulfill the San Diego criteria. These differences are significant in determining whether or not to seek other causes for sicca symptoms, and are critical in interpreting studies regarding the prevalence of clinical findings and the results of therapeutic trials.
Subjectively decreased tear production can be objectively documented with the Schirmer test. A strip of filter paper is placed into the lower conjunctival sac and the degree of wetting measured over a 5-minute period of time. Values of < 8 mm are judged highly suspicious, and values of < 2 mm are confirmatory of dry eyes. The Rose Bengal stain, which detects devitalized tissue, together with a slit lamp examination, is very useful in detecting Sjogrens patients whose ocular dryness is of sufficient severity to produce disruption in the integrity of the corneal and conjunctival epithelium (keratoconjunctivitis sicca and filamentary keratitis).
Quantitative testing for oral dryness is limited. Salivary scintigraphy may be performed on the parotid and submandibular salivary glands to assess their function. Sialography, utilizing intraductal injection of a water-based contrast agent, may demonstrate tortuous, ectatic salivary gland ducts. Biopsy of the major salivary glands is not routinely indicated, but a lip biopsy demonstrating lymphocytic aggregates of 50 or more cells in the periductal region of minor salivary glands has been judged to be the gold standard for the diagnosis of SS. False-positive results may be seen if the biopsy is obtained through inflamed, rather than normal, oral mucosa. Sample error in the performance of lip biopsies is problematic, yielding false-negative results.
The detection of rheumatoid factor and antinuclear antibodies, at a significant titer, supports the diagnosis of a systemic autoimmune process, rather than a local phenomenon. Some investigators have employed the presence of the more specific anti-Ro (SS-A) and anti-La (SS-B) antibodies as diagnostic criteria for the presence of SS, though neither is disease-specific.
The differential diagnosis of SS must exclude medications and other disorders that may cause sicca symptoms. Medications with significant anti-cholinergic side effects, but given for a variety of indications including management of respiratory secretions, or treatment of depression, fibromyalgia, sleep disorders, blood pressure, cardiac dysrrhythmias, gastrointestinal disorders, psychiatric disorders, or Parkinsonism may cause or exacerbate symptoms. Disorders which may cause sicca symptoms mimicking SS, include infiltrative processes (e.g. amyloidosis, lymphoma, sarcoidosis, and graft-versus-host disease), infectious processes (e.g. hepatitis B and C, HIV and other retroviruses, syphilis, and tuberculosis), autonomic and other neuropathies (e.g. age-associated, drug-induced, and multiple sclerosis), post-radiation changes, fibromyalgia, and the normal decrease in tear and saliva production seen with aging.
