Article: An evaluation of urine CCA strip test/SEA ELISA

Question 1

Urinary schistomoiasis background:

Answer 1

1) Caused by Schistosoma hematobium
2) Endemic on Zanzibar islands Unguja and Pemba
3) Endemic area depends on whether intermediate host snail is found or not: Bulinus globosus snail
- In Unguja often its a restricted area: but travellers carry it, possibly from Pemba too

Question 2

Kick out Schistomoiasis?

Answer 2

-Once they realised this geographical restriction: They started a limited area campaign called “Kick Out Schistomoiasis”
Kick Out Schistomoiasis did MDA to school kids:
-Praziquantel to kill urinary schisto
-Albendazole also to control soil-transmitted helminths in general
Also, they provided monitoring/surveillance of kids by Helminth Control Lab Unguja
Problems: -detecting Schisto was too hard, so implementing control programs was hard, alternative detection methods needed

Question 3

Evaluating alternative detection techniques for schisto? (and what Kick out Schisto did for it?)

Answer 3

1) they tried both more logistically hard approaches: measuring excreted urine-albumin
2) or easier/larger scale approaches: check micro-hematuria with urine strips
They evaluated everything as the program improves:
eg. They found that commercially available urine circulating-cathodic-antigen (CCA) dipstick (for both urinary and intestinal Schisto) does not detect S. hametobium, %50 sensitivity only in Ethiopia
Its reformulated now
3) Only recently most labs can use Ab-SEA(soluble egg antigen) ELISA
And a kit is developed for Schistosome mansoni

Question 4

Why CCA dipstick test would be useful? (pros/cons)

Answer 4

-Easily accessible by people (self-test)
-No labor/technician/skill required
-Most cost-efficient method (no laboratory/no workers)
-No electricity is needed
-CCA is only released from living worms (active infection/worm burden)
Cons:
-Observer dependent (is the band there or not?)
-Might not work at all, might not be specific enough between species either

Question 5

Why SEA ELISA Ab kit would be useful? (pros/cons)

Answer 5

Compared to regular ELISA:
1) Only very small fingerprick blood is enough to measure IgGs, not invasive for patients
2) Once you complete the analysis, HRP is connected to another color reagent which turns yellow: no need for a plate reader
Cons:
-Often Schisto Igs might not be differentiated between different species of Schisto/or even other helminth infections
-Too little blood gives no chance to repeat the experiment either
-They like ELISA in travelers: but egg secretion in Schisto might be variable
-Not sensitive for chronic Schisto or immunocompromised

Question 6

Materials methods (Study group)

Answer 6

Study group:
5 schools from Kick Out Schisto program is selected in Unguja:
-Kinyasini/Mwera: high transmission
-Kiboje/Kilombero: medium transmission
-Muyuni: Low transm.
study done after 11 months of last MDA (so not much effect of drugs) - treatment coverage also differs between different kids
Age: 8-14 years

Question 7

Materials methods

Answer 7

Microscopy: Mid-morning urine specimen
Urine CCA strip: Urine+ buffer with Abs are mixed = after 40 mins strip is compared to the other control strips / negative: visible or weaker than a threshold, while internal control was visible
SEA-ELISA: Blood collected on eppendorf + centrifuged, then ELISA
Final color was recorded w two observers: positive (light yellow) - strong positive (dark yellow)

Question 8

Results: (infection rates confirmed w microscopy)

Answer 8

Overall S. hametobium: %30.7 positive (microscopy)
Kinyasini Mwera high: %53.3 each
Kilombero: 33.3% / Kiboje: 10% = middle
Muyuni:%3.3
Children outside the endemic were 12.2 times less likely to get S. hematobium
Most kids were not really local to that area and lived there all their lives (travel, other school history)

Question 9

Results: Urine CCA strip

Answer 9

The test is useless, it barely finds something, finds %6 out of %55
Sensitivity: %9 lmao: can’t be used as a predictive tool in schools
Reformulation didn’t work: the previous one was kind of same
BUT: It worked really well on another area, Tanzania with high specificity and sensitivity
-It’s not clear why CCA ELISA works, but CCA strips do not? But definitely an effect of strain differences in different areas is observed in detection
-Also this strip works on intestinal schisto: therefore CCA on urinary schisto on kids are below the detection threshold, whereas in intestinal schisto it does not

Question 10

Results: SEA Ab ELISA

Answer 10

Found much higher levels of S. hametobium:
almost %90 at Kinyasini
Kilombero: %45
Mwera: %67
Kiboje: %27
All population: %48
SEA-ELISA and increasing egg count correlates directly
When microscopy is considered as “gold standard”: high sensitivity and specificity, although negative predictive value was low (as expected, bcs ELISA found more infected kids)
When SEA ELISA is considered as gold standard: specificity was low, apparently its a problem in parasitological methods - it definitely catches more infections than microscopy tho
SEA ELISA-microscopy results also correlate
SEA ELISA-and microhematuria results correlate