Background/Purpose:

Results of serologic tests for autoantibodies, including tests for Antinuclear antibodies (ANAs) and antibodies to specific nuclear antigens such as double-stranded DNA (dsDNA), play an important role in the diagnosis of connective tissue disorders (CTDs) such as systemic lupus erythematosus (SLE). ANAs are often detected in many healthy individuals without CTDs (~13%). Although a negative ANA test makes SLE highly unlikely, the positive results without significant clinical and laboratory features will lead to inappropriate tests and misdiagnoses.

Methods:

This is a retrospective chart review of patients on whom ANA test has been performed at a 330-bed community hospital in U.S. over a period of one year. All relevant details like demographics, locations, physician service, clinical features, history of CTDs, prior ANA results, additional tests and their results were noted. The justification for ordering the ANA test was compared against clinical and laboratory parameters included in the 2012 SLICC classification criteria for SLE.

Subsequently, true and false positive incidence was calculated. For all the negative or positive ANA tests, special attention was given to the indications of testing based on chart analysis. The 2012 SLICC clinical classification criteria were applied retrospectively to all cases regardless the ANA results; more than two positive parameters by SLICC criteria were proposed as a justification to order ANA test. The results are compared using 2×2 chi-square test.

Results:

During one year period, ANA was ordered for a total of 465 patients (Male=151, Female=314). Among them, 12.47% (n=58) had prior history of CTDs and 0.98% (n=4) had prior ANA positivity. In the remaining 403 patients, ANA was found positive (titers ≥1:80) in 6.94% (n=28) and negative in 93.05% (n=375). By applying 2×2 chi-square test, was shown  that ANA positivity or diagnosis of CTD is very unlikely if less than 2 SLICC parameters are present with a  p value <0.05 (Table 1)

Out of all 465 cases, only one new case of Anti phospholipid antibody syndrome was identified. A total of $39,297 was spent on ANA, and $87,165 on additional tests ordered in conjunction or following a positive ANA. It was noted that a large number of cases where ANA sub-serologies are ordered without knowing the ANA. This ordering pattern is against recommendation by “Choosing Wisely” campaign endorsed by ABIM and ACR.  

Conclusion:

Testing for ANA and related serology had cost approximately $126,000/yr for a medium size hospital and lead to no new SLE cases. ANA sub-serologies had cost the hospital $87,165 and according to “Choosing Wisely” campaign, were not indicated in more than 93% of cases, as these were negative ANA by IIF. In our hospital the lab was instructed to cancel the additional sub-serologies unless the ANA turns positive.

Table 1.

The Chi-Score statistic is 4.2058. The P value is 0.040287. The result is significant at p<0.05