Chicago Sky Blue May be Considered as a Diagnostic Stain for Visualizing Demodex in Patients With Demodex Blepharitis

Chicago sky blue is a promising stain that can identify and quantify the number of Demodex mites in patients with Demodex blepharitis, according to a study published in PeerJ.

“The process of staining and examining under light microscopy remains challenging in real-life practice since eyelashes are, de facto, lightweight and easily blown away causing loss of specimen,” explained Lunla Udomwech, Department of Ophthalmology, School of Medicine, Walailak University, Thasala, Nakhon Si Thammarat, Thailand, and coauthors.

The researchers developed a new staining product composed of Chicago sky blue stain in a gel mixture to solve the issue. They conducted a cross-sectional study at the dermatology and ophthalmology clinics at Walailak University, Thailand, between April and July 2022, to investigate the effectiveness of the new stain as a diagnostic method for Demodex blepharitis.

The study involved 30 participants, predominantly female (83.3%), with a median age of 64 years (IQR, 52.0–68.0) and a mean BMI of 23.3 (SD 2.8). A significant portion reported comorbidities, including dyslipidemia (50.0%), hypertension (36.7%), type II diabetes (6.7%), and cerebrovascular disease (10.0%).

The study assessed the efficacy of Chicago sky blue gel in detecting Demodex mites, showing a substantial increase in the positive detection rate from 56.7% to 100.0% by investigator A and from 66.7% to 88.3% by investigator B after applying Chicago sky blue gel. Bland-Altman analysis demonstrated high concordance between the two assessment methods by investigators, with rates of 90.0% and 93.3%. The median Demodex counts by investigator A increased from 1.0 (IQR, 0.0–1.0; range, 0.0–4.0) to 2.5 (IQR, 2.0–3.0; range, 0.0–7.0) post- Chicago sky blue gel application (P<0.001), and by investigator B from 1.0 (IQR, 0.0–1.0; range, 0.0–2.0) to 2.0 (IQR, 1.0–3.0; range, 0.0–6.0) (P<0.001). The correlation of Demodex counts between investigators was moderate before Chicago sky blue gel addition (r=0.51, P=0.004) and very strong after (r=0.92, P<0.001), indicating Chicago sky blue gel significantly improves the identification and quantification of Demodex mites.

“We found that Chicago sky blue gel significantly enhances the visualization of Demodex mites both in the naïve and expert investigators with a very strong correlation of mite counts,” concluded the study authors.

Reference

Udomwech L, Tawanwongsri W, Mordmuang A. Chicago sky blue gel for better visualization of Demodex in patients with Demodex blepharitis. PeerJ. 2023;11:e16378. doi:10.7717/peerj.16378