CD4/CD8 Ratio in Aqueous Humor in Uveitis

Dear Editor,

We present a case series report with a simple and reproducible method for anterior uveitis investigation. This method uses the CD4/CD8 ratio in aqueous humor, analyzed by flow cytometry, in patients with an acute episode of anterior uveitis. The characterization of different T-lymphocyte populations (CD4 and CD8) during an ocular inflammation episode may be useful, especially in uveitis with T-lymphocyte involvement and difficult diagnosis, such as virus uveitis, sarcoidosis, and masquerade syndromes in T lymphomas.

CD4/CD8 ratio in broncho alveolar lavage (BAL) is used for diagnosis of sarcoidosis, especially in sarcoidosis with lung involvement. It has been reported that a CD4/CD8 ratio of 3.5 or greater had a sensitivity of 52% and specificity of 94% for sarcoidosis.1 However, the CD4/CD8 ratio in BAL may be decreased in the 7–10% of patients with sarcoidosis.1 Thus, an elevated CD4/CD8 ratio may confirm the clinical suspicion of sarcoidosis, but a low ratio cannot be used to exclude the diagnosis of sarcoidosis. Recently, Kojima et al.2 published the diagnostic value of the CD4/CD8 ratio in vitreous fluid in sarcoidosis. They observed that vitreal CD4/CD8 ratio higher than 3.5 is a high diagnostic parameter in ocular sarcoidosis, with 100% sensibility and 96.3% specificity.2 However, they do not mention the possibility of measuring the CD4/CD8 ratio in aqueous humor, an easier and cheaper method.

In this case series study we investigated the CD4/CD8 ratio in aqueous humors of 6 patients, who were at least 18 years of age. The study protocol complied with the provisions of the Declaration of Helsinki, which was reviewed and approved by the Ethics Committee of the La Fe University Hospital of Valencia, Spain, and informed consent was obtained from each subject.

The aqueous samples of the uveitis patients were collected under topical anesthesia, under sterile conditions by slit lamp with the aid of one drop of povidone iodine before and after puncturing the anterior chamber. Antibiotic prophylaxis was subsequently used for several days. Aqueous control samples were collected from the right eyes of the 3 healthy subjects, who underwent cataract surgery with no other ocular or systemic diseases as specimens. The aqueous humor samples of control subjects were collected with a 30-gauge needle before cataract surgery commenced. Undiluted aqueous samples of at least 0.1 mL were collected from each subject and immediately sent to the lab for analysis. A flow cytometry of the aqueous humor samples was performed to quantify the lymphocytes and the CD4/CD8 ratio.

We have analyzed the CD4/CD8 ratio in 0.1–0.2 mL of aqueous humor in 3 patients with uveitis (a 43-year-old woman with clinical suspicion of sarcoidosis; a 47-year-old man with idiopathic anterior uveitis; a 51-year-old man with idiopathic anterior uveitis) and 3 healthy, age-matched subjects (a 43-year-old woman; a 47-year-old man; a 51-year-old man).

No lymphocytes were detected in the aqueous humor of the 3 healthy subjects; on the other hand, the CD4/CD8 ratio was 1.2 and 1.4, respectively, in both idiopathic anterior uveitis, but the CD4/CD8 ratio was 29.6 in the 43-year-old woman with clinical suspicion of sarcoidosis. This patient presented with an uveo-parotid fever as clinical debut, and focal ocular lymphocytosis was confirmed in the aqueous humor (67% lymphocytosis [89% CD4 and 3% CD8]). Moreover, sarcoidosis diagnosis was confirmed later by positive gammagraphy (lambda pattern) and positive BAL. Thus, our results appear to show that the CD4/CD8 ratio in aqueous humor may be useful in patients with active ocular inflammation, and it may be especially useful in patients with ocular sarcoidosis.

We have observed that the CD4/CD8 ratio can be analyzed in aqueous humor. Anterior chamber puncture has the advantage of being quick and relatively straightforward to perform and can be carried out in an outpatient setting.3 Thus, it allows us to confirm the focal lymphocytosis observed in ocular sarcoidosis, avoiding pars plana vitrectomy. We know that only about 0.2 mL of fluid are obtained with anterior chamber puncture, and a false-negative result may occur if there is relatively mild inflammation at the anterior chamber.4 Therefore, we think that an aqueous humor sample should be taken during the acute phase of anterior uveitis. Otherwise, to obtain a larger sample (0.5–1 mL) of intraocular fluid, vitreous sampling is necessary, just as Kojima et al.2 have done in their study. However, we have been able to analyze the CD4/CD8 ratio with only 0.1–0.2 mL of aqueous humor in 6 subjects, 3 of them with acute anterior uveitis.

In the 1990s, Ohta et al.5,6 analyzed the characterization of lymphocyte populations in uveitis. They reported that memory T-lymphocyte population (CD4⁺CD45RO⁺) is increased in aqueous humor in uveitis. In addition, they observed an elevated concentration of CD4 and CD8 lymphocytes in the aqueous humor of patients with uveitis, compared with their peripheral blood and compared with the aqueous humor samples of healthy subjects. Ohta et al.6 also commented that CD4 proportion was elevated in the aqueous humor of patients with ocular sarcoidosis (9 patients). However, they did not comment on the CD4/CD8 ratio in aqueous humor and its diagnostic value in ocular sarcoidosis.

We would like to briefly mention the main limitations of our case series report: its small sample size, the impossibility of establishing a statistical comparison, and the lack of comparison of CD4/CD8 ratio in aqueous humor with CD4/CD8 ratio in peripheral blood. Further studies are needed to confirm these preliminary observations; however, we think our preliminary data may be interesting and potentially relevant to future studies and clinical practice.

To conclude, we are presenting a simple, inexpensive, nonsurgical, and accessible method of CD4/CD8 ratio analysis in aqueous humor in uveitis patients, which might be especially useful in patients with ocular sarcoidosis.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.