Table 1.
Microscopy-based diagnostic methods for soil-transmitted helminths diagnosis.
| Microscopy-based techniques | Procedure | Outcome | Sensitivity | Negative Predictive Value | Advantages | Limitation | References |
|---|---|---|---|---|---|---|---|
| Direct wet mount Microscopy | Preparation of stool sample with one drop of saline/iodine on a microscopic slide with a cover glass. | Egg detection | Sensitivity: A. lumbricoides 83.3% and Hookworm 85.7% Sensitivity: Hookworm: 37.9 %, A. lumbricoides 52% and T. trichiura 12.5% |
Hookworm 97.5% and A. lumbricoides 98.8% | Low cost, easy and able to detect motile trophozoite | Low sensitivity | (Demeke et al., 2021; Dana et al., 2020; Else et al., 2020; Mengist et al., 2018 ; Nikolay et al., 2014; Endris et al., 2012) |
| Formol-ether concentration (FEC) | The stool sample is added to 7 mL of 10% formalin and the suspension is filtered through a sieve into a 15 mL conical centrifuge tube. Then, 4 mL diethyl ether is added to the formalin solution and centrifuged at 300 rpm for 1 min. The supernatant is discarded and the smear is prepared using a slide from the sediment. The sediment is screened under a microscope. | Egg detection | Sensitivity: A. lumbricoides 32.5% hookworm 64.2% and T. trichiura 75% Sensitivity: A. lumbricoides 81.4% hookworm 72.4% and T. trichiura 57.8% |
A. lumbricoides 94.7%, hookworm 84.5% and T. trichiura 75% A. lumbricoides 93%, hookworm 97% and T. trichiura 91.5% |
Low cost Essential for helminths ova detection | Need for centrifugation and does not detect unembryonated eggs of Ascaris spp. | (Hailu et al., 2022; Demeke et al., 2021; Else et al., 2020; Fenta et al., 2020; Sam et al., 2018; Endris et al., 2012) |
| Kato-Katz | The stool sample is pressed through a mesh screen to remove particles and an amount of sieved stool sample is placed into the hole of the template on a slide. Then, the template is removed and the remaining sample is covered with cellophane which is previously immersed with Glycerol-malachite green. The sample is screened under a microscope after 30 min and the eggs are counted. | Egg detection and egg quantification | Sensitivity: A. lumbricoides 93.1 %, hookworm 69% and T. trichiura 90.6% Sensitivity: A. lumbricoides 50%, hookworm 55.7% and T. trichiura 75% Sensitivity: A. lumbricoides 73%, hookworm 75.3% and T. trichiura 90.9% Sensitivity: A. lumbricoides 89.8%, hookworm 89.1% and T. trichiura 96.1% |
A. lumbricoides 97.3%, hookworm 97.3% and T. trichiura 98% A. lumbricoides 96%, hookworm 81.5% and T. trichiura 99.8% |
WHO recommended gold standard, lowcost, possible to determine the burden of infection | Low sensitivity, fails to detect infections of low intensity | (Khurana et al., 2021; Fenta et al., 2020; Cools et al., 2019; Moser et al., 2018; Endris et al., 2012) |
| McMaster | A known amount of stool is mixed with a saturated salt solution. The top layer of the solution is added to the reading chamber and the EPG count can easily be derived by multiplying the number of eggs under the marked areas by a simple conversion factor | Egg quantification | Sensitivity: A. lumbricoides 74.3%, hookworm 67.6% and T. trichiura94.6%
Sensitivity: A. lumbricoides 74.3%, hookworm 92.3% and T. trichiura 94.9% |
A. lumbricoides 82.4%, hookworm 62% and T. trichiura 47.8% | Inexpensive, easy, has been extensively used in human studies for estimation of anthelmintic cure rates. Highly sensitive for low-intensity soil-transmitted helminth infectionS |
Need for a special counting chamber | (Khurana et al., 2021; Manuel et al., 2021; Else et al., 2020; Albonico et al., 2013; Albonico et al., 2012) |
| FLOTAC | The FLOTAC apparatus is a cylindrical-shaped device made of polycarbonate amorphous thermoplastic with two flotation chambers. An amount of stool sample is homogenized and filtered with water or saline. The filtrate is mixed with a floatation solution and is added to the chambers. The chambers are centrifuged and examined under a microscope. | Egg quantification | Sensitivity: A. lumbricoides 81.9%, hookworm 80.% and T. trichiura 96.8% Sensitivity: A. lumbricoides 79.7%, hookworm 92.4.% and T. trichiura 91% |
A. lumbricoides 86.9%, hookworm 73.4% and T. trichiura 61.1% | Detection of different STHs simultaneously especially for low- intensity infections. | It is complex, a specific device is needed and requires centrifugation with two different rotors. | (Khurana etal., 2021; Manuel etal., 2021; Else etal.,2020; Knopp et al., 2014; Nikolay et al., 2014; Albonico et al., 2013; Cringoli et al.,2010) |
| Mini-FLOTAC | A weighed stool sample is homogenized with 5% formalin, filtered, and the filtrate is added to the flotation solution. The suspension is loaded into the two flotation chambers. Screened under a microscope after 5-10 min. | Egg quantification | Sensitivity: A. lumbricoides 42.1 %, hookworm 70.8.% and T. trichiura 85.6% Sensitivity: A. lumbricoides 75.5%, hookworm 79.2.% and T. trichiura76.2% |
Detection of different STHs simultaneously | It is complex and a specific device is needed. Less sensitive for the diagnosis of A. lumbricoides | (Khurana et al., 2021; Manuel et al., 2021; Else et al., 2020; Cools et al., 2019; Barda et al., 2013; Nikolay et al., 2014) | |
| Baermann Technique | A 10 g of stools is place over few layers of gauze inserted into a cup filled with tap water. The apparatus is expose to artificial light directed at the funnel's bottom. Then 50 ml of the liquid is collected from the bottom of funnel in a plastic tube after 2 hours and centrifuged at 500 g for 2 minutes. A water suction pump use to drain the supernatant. | Larvae detection | Sensitivity: S. stercoralis 16% Sensitivity: S. stercoralis 20.7% Sensitivity: 28.3% and specificity of 75.2% |
Highest sensitivities for S. stercoralis and detected larvae can be identified more easily Nearly 4 times higher sensitivity than FEC | Time consuming, large quantity of stool required, fresh sample required. | (Khurana etal., 2021 ;Hailegebriel et al., 2017; Knopp et al., 2014; Carvaho et al., 2012; Machicadoet al., 2012; Knopp et al., 2008) | |
| FECPAKG2 | The FECPAKG2 platform, which includes a cassette, focuses helminth eggs into a single microscopic field of vision, which is captured and saved on a computer, allowing the eggs to be counted. | Egg quantification | Sensitivity: A. lumbricoides 75.6%, hookworm 71.5%, and T. trichiura 65.8% | Detection of different STH simultaneously, simple procedure with a result within an hour | Internet connection is required | (Manuel et al., 2021; Else et al., 2020; Cools et al., 2019; Moser et al., 2018) |