Evaluation of hen’s egg white for fixation of concentrated sputum smears for acid-fast bacilli microscopy

Abstract

Laboratory diagnostic method of acid-fast bacilli (AFB) using smear microscopy for tuberculosis (TB) diagnosis can be increased the sensitivity by sputum concentration technique. The concentrated sputum smear may be peeled off that is a weak point of this technique. Thus this experimental study was aimed to evaluate the using of hen’s egg white for fixation of concentrated sputum smears for AFB examination. 280 concentrated sputum samples were used for comparing between unfixed smear and egg white-fixed smear techniques. The unfixed smear technique had 26.1% of peeling, while egg white-fixed smear technique had no peeling (P-value < 0.001). For positive rate of AFB examination, egg white-fixed smear technique yielded 50.0%, whereas unfixed smear technique yielded 38.2% (P-value = 0.005). The storage time testing of egg white at ≤ 30 days, 31-60 days and 61-90 days had no statistically significant difference in AFB results of concentrated smear (P-value = 0.986). Therefore, fixation of concentrated sputum smear with egg white is useful for preventing the peeling of smear, increasing AFB-positive rate and saving the cost of smear in no repeating. Because hen’s egg is not expensive and egg white can be stored for at least 3 months, this smear fixation technique is so suitable for TB laboratory.