Demodex diagnosis: To pluck or not to pluck
Studying your lashes right where they are is as good as, and maybe better than, pulling them out and looking at them on a slide.
If it’s all the same to you, I prefer to keep my lashes, thank you very much.
The Clinical Use of Eyelash Manipulation in the Diagnosis of Demodex folliculorum Blepharitis.
Murphy et al, Eye and Contact Lens, April 2019
To compare the efficacy of using an eyelash manipulation technique to the traditional eyelash epilation and subsequent microscopic examination technique, when investigating for the presence of Demodex folliculorum in a clinical setting.
Four hundred twenty-eight eyelashes of 107 subjects were chosen to compare the quantity of D. folliculorum visible on eyelash manipulation with the slitlamp biomicroscope to that counted on microscopic examination of the same epilated eyelash. One eyelash from each eyelid was rotated with sterile forceps in situ, and the number of D. folliculorum seen emerging from the follicle was counted. The same eyelash was then epilated, and the number of D. folliculorum on the epilated eyelash was counted. Data were analyzed to check for agreement between the two techniques.
Intraclass correlation coefficient showed moderately good agreement for assessing the quantity of D. folliculorum (0.78) between the techniques. However, the Bland-Altman plot suggested that consistently higher quantities were found on eyelash manipulation. The overall mean quantity of D. folliculorum was also greater on eyelash manipulation (1.45 mites; range, 0-13 mites) than on microscopic examination of the epilated eyelash (0.81 mites; range, 0-16; P= <0.001). Weighted kappa (κw=0.56) indicated weak levels of agreement between the two methods for addressing severity of infestation.
Eyelash manipulation exhibited larger quantities of D. folliculorum than complete epilation of the eyelash. In a clinical setting, complete eyelash epilation is not necessary to accurately detect Demodex blepharitis requiring treatment.
On the other hand…
If you want to go for the gold, in terms of both quality and cost, you could go really super high-tech and use a confocal microscope (probably not at your friendly neighborhood optometrist’s office!) to diagnose the little buggers.
Prospective study of the diagnostic accuracy of the in vivo laser scanning confocal microscope for ocular demodicosis.
Wang et al, American Journal of Ophthalmology, March 2019
To determine the diagnostic accuracy of in vivo confocal microscopy (IVCM) for ocular demodicosis DESIGN: Reliability and Validity analysis.
Setting: Single-center study.
Consecutive patients presenting to Zhongnan Hospital of Wuhan University, Hubei, China, between February 2017 and February 2018 with blepharitis.
Following examination, the blepharitis was scanned by IVCM. The regrading of the shuffled image set was performed by grader 1(experienced) and grader 2 (inexperienced). The regrading of the shuffled image set was performed by 2 graders 3 weeks later. eyelash samples were collected for light microscopy.
MAIN OUTCOME MEASURES:
The main outcome measures were sensitivity, specificity, and positive and negative predictive values of IVCM compared with those of positive light microscopy under two definitions. Sensitivities and specificities for multiple graders were pooled and 95% confidence intervals calculated.
Sensitivity of IVCM grader 1 and grader 2 based on the definition of "light microscopy-positive demodex" was 100% (95% CI: 94.84%∼100%), 98.8% (95% CI: 93.02%∼99.94%), respectively. Sensitivity of IVCM grader 1, grader 2 and light microscopy to the definition of "definite diagnosis demodex" definition Was 100% (95% CI: 97.02%∼100%), 93.63% (95% CI: 88.28%∼96.73%), and 56.69% (95% CI: 48.55%∼64.49%).
IVCM is better than traditional methods in detecting the number and sensitivity of demodex, and it is both highly sensitive and specific when performed by an experienced operator.