Table 2. Kappa coefficient’s agreement interpretation.

Kappa coefficient *	Interpretation
0	No agreement
0.10–0.20	Slight agreement
0.21–0.40	Fair agreement
0.41–0.60	Moderate agreement
0.61–0.80	Substantial agreement
0.81–0.99	Near perfect agreement
1	Perfect agreement

* Kappa value calculations: k = (po–pe) / (1 –pe)

po: Relative observed agreement between self -testing and testing by professional user

pe: Hypothetical probability of chance agreement