Objective: A novel artificial sputum has been developed using polyacrylamide, cultured THP-1 cell and BCG-Pasteur. Smears prepared with this artificial sputum are similar to actual sputum and has feasibility to set any positivity grades. Long-term storage and reproducibility of the positivity was examined to support further availability.
Method: The artificial sputa were stored for up to 9 months at room temperature, 4 degrees C and -20 degrees C. Then, smears were prepared and their macroscopic and microscopic appearance were examined compared with smears from freshly prepared artificial sputum. Furthermore, smears with different positivities (+/-, 1 +, 2 + and 3 +) were prepared and examined by several trained technicians, and the reproducibility of the original sputum positivity was determined.
Results: Macroscopic and microscopic appearance of smears prepared from long-term stored artificial sputum showed little changes compared with smears of freshly prepared artificial sputum. The positivity of these smears fell in their original grade. A total of 91 smears were prepared from artificial sputum with different positivity and examined by trained technicians. Although 3 out of 36 +/- smears were determined as negative, all of the remaining smears were evaluated correctly.
Discussion: This study confirmed that the artificial sputum and the smears have long-term storage stability and reproducibility in the positivity. These results suggest that the artificial sputum can be widely used to perform external quality assessment in many countries, including high prevalence countries.