Clinical guide needed to improve management of cat-scratch disease

11 Nov 2020
Relevant authorities have been running inspections on stray and pet dogs and cats.
Relevant authorities have been running inspections on stray and pet dogs and cats.

Certain concerns have been raised regarding the serologic diagnosis of cat-scratch disease (CSD), which include the use of low titres for positivity, incomplete diagnostic evaluation, and the lack of convalescent serologic testing, reveals a study.

“We propose a clinical guide to assist in managing suspected cases of CSD,” the authors said.

A retrospective chart review of immunocompetent paediatric patients was carried out at the Hospital for Sick Children in Toronto, Canada, spanning a period of 11 years. In total, 154 cases were included with serologic titres ≥1:128. These were further divided into the following groups: group 1=1:128; group 2=1:256; and group 3 ≥1:512.

The authors evaluated cases within groups with respect to cat contact, clinical presentation, further testing, and final diagnosis.

Among patients with a titre of 1:128, one-third had an alternative diagnosis. Most patients with a titre of 1:128 or 1:256 did not undergo convalescent serologic testing. Only one case within these two groups had a fourfold rise in the convalescent titre.

Furthermore, there was a trend of decreasing number of patients with alternative diagnoses (p=0.03) and increasing number of patients presenting with regional lymphadenopathy (p=0.07) which correlated with higher titres in group 3 compared with group 1.

Bartonella henselae serology is commonly used to diagnose CSD, with titres above a threshold for positivity suggesting either a recent or remote infection. A fourfold increase in the convalescent titre in some cases could confirm a recent infection.

“Many atypical presentations attributed to CSD utilize a low threshold for positivity without supportive evidence from convalescent sera or supplemental testing, raising a concern for the overdiagnosis of CSD,” the authors said.

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