We compared the correlation between stage as determined by CXR and that determined by 99mTc-DP scanning with the к statistic. A к statistic of > 0.8 is considered to represent strong agreement. Continuous data are reported as the mean ± SD. We utilized the Student t test to analyze continuous variables. The x2 test was employed to compare categoric variables except in cases in which the expected values were small. In these instances, we relied on the Fisher exact test. All tests were two-tailed, and a p value of < 0.05 was assumed to represent statistical significance. Ninety-five percent CIs are reported where appropriate. Analyses were done using a statistical software package (SPSS, version 10.0; SPSS; Chicago, IL). To determine our sample size for this pilot study, we assumed that the findings of 99mTc-DP scans would be positive in 70% of patients. Setting the CI around that estimate of the prevalence to be ± 20%, we calculated that we would require 20 subjects.
The study cohort included 22 subjects. As shown in Table 1, the mean age was 41.3 ± 9.3 years, and approximately 40% of the patients were female. The population was evenly divided between African Americans and whites. The mean duration of sarcoidosis prior to enrollment was 4.2 ± 3.1 years. Six subjects were receiving treatment for sarcoidosis when the 99mTc-DP scans were obtained. The therapeutic agents utilized included corticosteroids (three patients), methotrexate (two patients), and infliximab (three patients), with several individuals having been treated with combination regimens. Radiographically, the most common CXR stage was stage I and was seen in 54.5% of cases.
99mTc-DP scans showed uptake in the chest in 81.8% of patients (95% CI, 59.7 to 94.8%). Among the four patients without evidence of activity on 99mTc-DP images, the CXR findings of all had normalized since they had received the initial diagnosis of sarcoidosis. In other words, all patients with abnormal CXRs had evidence of uptake by 99mTc-DP scanning. Patterns of 99mTc-DP activity noted on 99mTc-DP images generally conformed to the accepted staging system for sarcoidosis (Fig 1, 2). We failed to note patterns of DP uptake that mimicked either the lambda or panda patterns described with Ga scintigraphy.
Figure 1. Coronal images of the chest demonstrate intense, focal, bilateral hilar 99mTc-DP uptake.
Figure 2. Axial and coronal images of the chest demonstrate bilateral, diffuse, increased parenchymal lung uptake.
Table 1—Subject Characteristics (n = 22)
|Age, yr||41.3 ± 9.3|
|Currently receiving therapy for sarcoidosis||27.3|