Current Diagnostic Tools for Chikungunya May Not Be Reliable in Older Population of Patients

As mosquito-borne viruses such as Zika, Dengue, Chikungunya continue to pose a significant public health challenge, the need for reliable diagnostic tools for patient assessment is paramount.

Unfortunately, available diagnostic platforms are not one-size-fits-all—at least if the results of a study published online January 5th by the journal PLOS Neglected Tropical Diseases are any indication.

Researchers in the departments of geriatrics and virology at the University Hospitals of Martinique in Martinique, France, where, as in much of the Caribbean, diseases such as Chikungunya have proved particularly problematic, evaluated the accuracy of 2 screening protocols for the mosquito-borne virus in a subset of patients 65 years of age and older in a retrospective case analysis: the Mayotte tool developed by Sissoko et al and the Reunion Island tool developed by Thiberville et al. As the authors note, earlier research suggests that Chikungunya mortality may be up to 5 times higher in those 65 years or older, due to “atypical presentation” and comorbidities, and the 2 screening protocols were initially evaluated in younger populations (average age: 27.2 and 40.1 years, respectively).

The Mayotte tool uses the presence of simultaneous fever and incapacitating polyarthralgia as its key diagnostic marker, while the Reunion Island tool uses the presence of simultaneous fever and arthralgia. Unfortunately, older individuals infected with Chikungunya do not always present with either symptom pair, according to the Martinique-based research team.

Indeed, for the PLOS Neglected Tropical Diseases report, the cases studied involved 687 patients 65 years and older (average age 80.4 years) who had been admitted to acute care units at University Hospitals for suspected Chikungunya virus infection (confirmed via biological testing using Reverse Transcription Polymerase Chain Reaction) in 2014. Of the patients included in the analysis, 68% had confirmed Chikungunya virus infection.

In all, the most commonly identified symptoms were fever (73.1% of patients) and arthralgia (51.4% of patients). As diagnostic markers, based on these findings, the authors determined that these 2 symptoms had sensitivity ranging from 6% (fever and headache) to 49% (fever and polyarthralgia). Youden’s index for these symptoms ranged from 1% (fever and headache) to 30% (fever and polyarthralgia). Positive predictive value and negative predictive value ranged from 70% to 95%, and from 32% to 43%, respectively.

Overall, specificity of the Mayotte tool was just 81% and specificity of the Reunion Island tool was 95%; sensitivities for the 2 tools were just 49% and 23%, respectively. While Sissoko et al found that fever plus polyarthralgia was present in 83.6% of their study patients, for example, the Martinique team found that the combination was present in just 48.6% of their older patients.

The authors of the PLOS Neglected Tropical Diseases report did not respond to requests for comment. However, in their concluding remarks, they note, “Our study shows that the diagnostic performance of 2 scores to screen for potential CVI, both developed in younger populations, is poor among older patients, as shown by the associated Youden’s index. While the specificity and the [positive predictive value] of the scores are good to excellent, the sensitivity and [negative predictive value] are mediocre, not to say poor… [This is] likely due to the different clinical profiles observed in elderly subjects, which renders the use of scores developed in young populations perilous.”

Brian P. Dunleavy is a medical writer and editor based in New York. His work has appeared in numerous healthcare-related publications. He is the former editor of Infectious Disease Special Edition.