Comparison of salivary hemoglobin measurements for periodontitis screening

Salivary hemoglobin (Hb) for screening of periodontitis is approved under the pharmaceutical affairs law of Japan. Two reagents are commercially available for the modified fecal occult blood test: Saliva Hemo Plus and OC-AUTO S Latex Reagent. We simultaneously measured split specimens from 561 samples by using these two methods and compared the differences and agreement between both methods. Moreover, saliva samples were collected from 10 subjects at five time points during the day for analysis of circadian variations and fluctuation. The Pearson's correlation coefficient for these two reagents was 0.794. The Bland-Altman plot of differences in salivary Hb levels measured by the two reagents indicated that the difference included fixed errors (0.55 μg/mL). On analysis of circadian variations, no statistically significant differences were observed using the Friedman test. However, fixed errors were observed between wake-up time and before dinner and before lunch and before dinner, and no random errors were observed by Bland-Altman analysis. In conclusion, the salivary Hb levels measured using OC-AUTO S Latex Reagent were lower than those measured using Saliva Hemo Plus, along with a tendency for higher levels in the morning. Thus, when performing salivary tests these observations must be considered.