Development and validation of the AF score for diagnosis of adult-onset Still's disease in fever of unknown origin

Objective

To develop and validate a diagnostic score to identify adult-onset Still's disease (AOSD) in fever of unknown origin (FUO).

Methods

A single center, retrospective case-control study of inpatients with FUO from January 2018 to December 2021. Using clinical and laboratory data from 178 cases with AOSD and 486 cases with FUO, we developed an AOSD/FUO (AF) score with a Bayesian Model Averaging approach. AF score and Yamaguchi's criteria were evaluated by sensitivity, specificity, accuracy, and positive/negative predictive value for diagnosis of AOSD in developmental and validation samples.

Results

Persistent pruritic eruptions (PPEs) in patients with rashes was higher in AOSD group than FUO group (52.3% vs 7.4%; P < 0.01). PPEs yielded a specificity of 97.5% and a sensitivity of 44.9%. AF score = PPEs × 3.795+Evanescent rash × 2.774+Serum ferritin × 1.678+Myalgia × 0.958+Neutrophil count × 0.185+Platelet count × 0.004. A cut-off value ≥ 5.245 revealed the maximizing sensitivity of 88.7% and specificity of 95.8% in discriminating AOSD from FUO in the validation group. And AF score improved the accuracy from 82.6% to 93.3% compared with Yamaguchi's criteria.

Conclusions

We developed and validated a new score which can identify AOSD in FUO with higher classification accuracy than Yamaguchi's criteria. Future multi-centric prospective studies need to be designed to confirm the diagnosis value of AF score.

Effect of adjusted cut-offs of interferon-γ release assays on diagnosis of tuberculosis in patients with fever of unknown origin

Background

Tuberculosis (TB) is a leading cause of fever of unknown origin (FUO). In recent years, interferon-γ release assays (IGRAs) have been widely utilized and the cut-off values given by the manufacturers are set in countries where rates of TB are not as high.

Methods

A prospective cohort study was conducted in a Chinese general hospital to evaluate the diagnostic performance of T-SPOT.TB (T-SPOT) and QuantiFERON-TB Gold (QFT) in detecting active TB (ATB) in a high TB endemic area. Test results were compared with the culture and clinically confirmed diagnosis. Further, we explored an alternative method of interpreting IGRAs by increasing the cut-off values.

Results

The sensitivity and specificity of T-SPOT in detecting ATB were 85.3% (95% CI 81.6–94.0%) and 71.8% (95% CI 67.3–76.0%), respectively. The sensitivity and specificity of QFT were 72.3% (95% CI 62.8–80.1%) and 77.0% (95% CI 72.7–80.8%), respectively. Receiver operating characteristic analysis was used for evaluation of different cut-off values. When the cut-off values were adjusted as 125 spot-forming cells (SFCs)/ 2.5*10⁵ cells for T-SPOT and 4.0 IU/ml for QFT, the specificity could be improved to > 90.0% (90.3% and 94.1%, respectively), and the sensitivity were 43.1% and 41.6%, respectively. The new adjusted cut-off values were validated in another independent validation cohort.

Conclusion

The adjusted cut-off values of the two assays considerably improved the diagnostic value when applied to FUO patients in clinical settings.

Extra pulmonary tuberculosis presenting as fever with massive splenomegaly and pancytopenia

Disseminated tuberculosis is an important differential diagnosis for fever of unknown origin (FUO) and it can present with hepatosplenomegaly and lymphadenopathy and may have meningitis and with hematological abnormalities including pancytopenia or a leukemoid reaction. We report the case of a 13-year old male who presented with fever, weight loss, pallor and massive splenomegaly with pancytopenia, in whom a bone marrow trephine biopsy showed caseating granulomata, who responded well to antituberculous treatment and has remained healthy on follow up after nine years.