Strongyloides stercoralis prevalence and diagnostics in Vientiane, Lao People’s Democratic Republic

Abstract

Background Despite the high prevalence of strongyloidiasis in the Laotian population, Laotian hospitals still lack diagnostic capacity to appropriately diagnose Strongyloides stercoralis infections. This cross-sectional hospital-based study was conducted to assess the prevalence of Strongyloides stercoralis infection among hospitalized patients treated at Mahosot Hospital, the primary reference hospital of Lao People’s Democratic Republic (Lao PDR), and to validate feasible methods for diagnosing S. stercoralis infection at hospital’s laboratory. Methods Between September and December 2018, stool samples of 104 inpatients were investigated for S. stercoralis infection by wet smear, Baermann technique, Koga Agar plate culture (KAPC), and real-time detection polymerase chain reaction (RTD-PCR) at the Infectious Diseases Ward of the Mahosot Hospital in Vientiane. The sensitivity, the specificity, the negative predictive value (NPV) of each diagnostic test, as well as their combination(s) was calculated using a composite reference standard (CRS). The correlation of the different test methods was assessed by chi-square or Fisher’s exact test. Cohen’s kappa coefficient was used to assess the diagnostic agreement of the different test methods. Results The overall prevalence of S. stercoralis infections among the study population was 33.4%. The cumulative infection prevalence statistically significantly increased from the lowest age group of 40 years and below (22.4%), to the medium (40.0%) and to the oldest age group of 61 year and above (72.7%)(P = 0.003). The cumulative infection prevalence of CRS was considerably higher in male (40.4%) compared to female patients (28.1%), but not statistically different (P = 0.184). The diagnostic sensitivity of Baermann technique, KAPC, RTD-PCR, and the combination of Baermann technique and KAPC were 60.0, 60.0, 74.3, and 77.1%, respectively. Only 13 patients (37.1%) of the total 35 S. stercoralis patients diagnosed with any technique had a simultaneously positive diagnostic test with Baermann, KAPC and RTD-PCR. Conclusions We identified Baermann technique and KAPC to be currently the most feasible and implementable standard methods for diagnosing S. stercoralis at a hospital setting such as Mahosot Hospital and provincial and district hospitals in Lao PDR and other low- and middle income countries in Southeast Asia. Trial registration This study was approved by the National Ethics Committee for Health Research in Lao PDR (reference no. 083/NECHR) and by the Ethics Committee Northwest and Central Switzerland (reference no. 2018–00594).

Evaluation of five diagnostic methods for Strongyloides stercoralis infection in Amhara National Regional State, northwest Ethiopia

“…A recent study showed that the detection rate of S. stercoralis could be increased when RT-PCR was used instead microscopy based methods [ 34 , 35 ]. In the present study, the detection rate of S. stercoralis by RT-PCR was 28.8%, which is lower than 36.2% previously reported [ 28 ], but it is higher than 13.4% in northwest Ethiopia [ 17 ], 6% in northern Australia [ 36 ], 25% in Lao People’s Democratic Republic [ 12 ]. The variation might be related to accuracy in DNA extraction, preservation and its amplification technique.…”

“…Among the methods used for the detection of eggs from stool specimens, direct saline microscopy [ 4 ], FECT [ 5 ] and STST [ 6 ] have the lowest sensitivity. The use of these methods for S. stercoralis detection might lead to misdiagnosis and underreporting of strongyloidiasis compared with BCT [ 7 ], APC [ 8 – 11 ], and RT-PCR or a combination of APC and BCT which have better detection rates [ 12 ]. Because of the low sensitivity of each method for larvae detection, a combination of methods is the most sensitive approach.…”

“…The two most sensitive parasitological methods for the diagnosis of S. stercoralis infection are BCT and APC, but they are not currently used as routine diagnostic techniques in health facilities in endemic countries [ 13 ]. A combination of these two methods is more sensitive than RT-PCR alone [ 12 ]. As a result, underdiagnosing and underreporting of S. stercoralis infection in endemic countries like Ethiopia is a common phenomenon [ 14 ].…”

A Practical Approach to Screening for Strongyloides stercoralis

“…Microscopy-based direct methods (such as simple wet-smear preparation or Kato-Katz) and even conventional concentration techniques (such as the formalin-ether concentration technique (FECT)) have low sensitivity because of the irregular and often low larval output in latent strongyloidiasis. Concentration techniques specifically designed for the detection of S. stercoralis (such as Baermann or Koga-agar plate-culture (KAPC)) provide more reliable and more sensitive results (each method has a sensitivity in immunocompetent patients of 60%, or 77% when combined) [4]. According to some studies, nucleic acid amplification tests (such as stool PCR) are considered to have better sensitivity than the concentration techniques [5], which are less user-dependent, but expensive and rarely available in low-and middle-income countries.…”

“…Repeated stool tests (up to three) are generally recommended to increase sensitivity, but this is often not performed because of logistical reasons; Baermann analysis should be performed within a short time after collection, and an interval of at least 72 h needs to be adhered to in between, making this unfeasible in the case of urgent immunosuppressive treatment [6]. If only a single stool sample is available, as is most often the case, our algorithm proposes assessment by stool PCR, KAPC and Baermann concentration in parallel, in order to increase the sensitivity of the diagnostic tests [4].…”