Comparison of laboratory techniques for diagnosis of hookworm infections

Abstract

INTRODUCTION: Hookworm infection may be diagnosed by detection of eggs or culturing of larvae from stools. OBJECTIVE: To compare the efficacy of modified Kato-Katz (K-K) technique, saline smears, Harada-Mori (H-M) and nutrient agar culture plate (NACP) methods in diagnosis of hookworm infections. METHODOLOGY: A total of 324 stool samples, from the plantation sector families in Ratnapura district were examined by modified Kato-Katz technique and saline smears, and cultured by Harada-Mori and on NACP according to standard protocols, at the Faculty of Medicine, Ragama. Harada-Mori and NACP were maintained for 7-10 days and larvae or larval tracts observed by a stereomicroscope. Positivity in any two of the four techniques was considered the gold standard positive. Statistical analysis was done using SPSS version 16. RESULTS: A total of 172 (53.1%) samples were positive by at least one method. The positivity rates with K-K, H-M, NACP and saline smears were 42.3% (137/324), 37.7% (122/324), 23.5% (76/324) and 22.2% (72/324) respectively. The highest sensitivity (89.8%) and lowest specificity (88.3%) was seen in modified K-K, the lowest sensitivity (50.4%) in saline smears and the highest specificity in NACP (98.5%). Detection rates with saline smears, H-M and NACP rose with increasing intensity of infection as determined by K-K technique. Harada-Mori had the highest detection rate (70.7%) in light infections. It also detected 11.8% of K-K negative samples. CONCLUSIONS: The modified K-K technique is a reasonably good diagnostic method for detection of hookworm infections. A combination of methods will increase the diagnostic accuracy in hookworm infections.