Investigation of SARS-CoV-2 on Ocular Surface of Coronavirus Disease 2019 Patients Using One-Step Reverse-Transcription Droplet Digital PCR

Figures & data

Table 1 Basic Clinical Characteristics of Enrolled Patients

Study Population	N(%)
No. of patients	68
Age, median (IQR), y	58.3(47–70)
Gender
Male	33(48.5)
Female	35(5.5)
Severity
General	55(81.9)
Severe	13(19.1)
Sampling lags^a
<10 days	14(20.6)
10–20 days	34(50)
>20 days	20(29.4)
Comorbidities	33(48.5)
Hypertension	25(36.8)
Diabetes	12(17.6)
Coronary heart disease	3(4.4)
CT Laterality
Unilateral	15(22.1)
Bilateral	53(77.9)

Note: ^aThe time from illness onset to the conjunctival sampling.

Figure 1 Evaluation of SARS-CoV-2 probe-primer set using plasmid standards. (A) Dilution curve of plasmid standards quantification by ddPCR. Correlation between expected and observed copy number were showed. Each black square represents a single replicate well of the dilution experiment, whereas the regression line is based on the average concentration at each dilution. (B) Probit analysis sigmoid curve reporting the lower limit of detection of ddPCR per reaction.

Figure 2 Comparison of positive rates of SARS-CoV-2 detection in tears using different methods.

Abbreviations: Real-time PCR, real-time polymerase chain reaction; RT-ddPCR, reverse-transcription droplet digital polymerase chain reaction; sampling lags, the time from illness onset to the conjunctival sampling.

Figure 3 Distribution features of SARS-CoV-2 in the blood, tears, and nasopharyngeal samples during COVID-19 pneumonia courses.

Abbreviations: Conj, conjunctival; NP, nasopharyngeal.

Table 2 Correlation Analysis of Positive One-Step RT-ddPCR Tear Specimens

Study Population (No.)	Conjunctival Positive	Conjunctival Negative	P-value
No. of patients	17	51
Gender			0.57
Male	9	23
Female	8	28
Severity			0.85
General	12	36
Severe	5	15
Age			0.22
<50 years	4	15
>50 years	13	36
Sampling lags			0.81
<10 days	4	9
10–20 days	7	20
>20 days	6	22
CT Laterality			0.61
Unilateral	3	12
Bilateral	14	39
Blood ddPCR^a			0.77
Positive	7	19
Negative	10	32
Nasopharyngeal qPCR^a			0.028*
Positive	7	8
Negative	10	43

Notes: ^aSamples acquired from the same day of conjunctival sampling; *P < 0.05.