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RDT Quiz A Q5: Difference between revisions

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|colspan="1" style = "font-size:130%; color:black; background: FFFAFA"|<span style="color:black>'''RDT Quiz A Q5'''</span>
|colspan="1" style = "font-size:130%; color:black; background: FFFAFA"|<span style="color:black>'''RDT Quiz A Q5'''</span>
</br><span style="font-size:90%">RDT tests use specific antibodies to identify the malaria species. Users often believe that these tests  are equally effective for diagnosing all species, but this is not true.</br></br></span>
</br><span style="font-size:90%">RDT tests use specific antibodies to identify the malaria species. Users often believe that it is not important to know which antibodies their own test uses. However, different antibodies are known to have particular strengths and weaknesses.</br></br></span>
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File:Mosquito.png|link={filepath:Mosquito.png}
File:2 RDT_work.jpg|<span style="font-size:80%">''Image from section "How RDT tests work"''</span>|link={{filepath:2 RDT_work.jpg}}
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<quiz display=simple>
<quiz display=simple>
{<span style="font-size:90%">For which malaria species do appropriate RDT tests have best sensitivity ('''make two selections''')?'''</br></br>
{<span style="font-size:90%">RDT tests that use antibodies that detect the malarial antigen HRP2 are widely used. Which of the statements below are true of HRP2 ('''select all that apply''')?'''</br></br>
|type="[]"}
|type="[]"}
+<span style="font-size:90%"> ''P.falciparum''
+<span style="font-size:90%"> The antigen identifies only ''P.falciparum''
+<span style="font-size:90%"> ''P.vivax''
-<span style="font-size:90%"> The antigen identifies ''P.vivax''
-<span style="font-size:90%"> ''P.ovale''
+<span style="font-size:90%"> ''HRP2'' gene-deletion may affect results
-<span style="font-size:90%"> ''P.malariae''
-<span style="font-size:90%"> Antibodies to pfLDH are more sensitive
-<span style="font-size:90%"> ''P.knowlesi''
+<span style="font-size:90%"> May be negative in severe infection
</quiz>
</quiz>


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! colspan="1" |<span style="font-size:90%">Explanation of correct answer (click "Expand").</span>
! colspan="1" |<span style="font-size:90%">Explanation of correct answer (click "Expand").</span>
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|-
|</b> <span style="font-size:90%">''Short answer taken from section "Main RDT page" (see the section for full details and links)''.</br></br>The different malaria species are detected with different sensitivity. The table below provides an overall summary of the sensitivity that can be expected for RDT tests (the specific section in the main section provides more detail)''.</span></br></br>
|<span style="font-size:90%">''Short answer taken from section "RDT test antigens" (see the section for full details and links)''.</br></br></span>
 
<span style="font-size:90%">P.falciparum parasites produce “histidine-rich” proteins (HRP). The HRP2 antigen is highly expressed and stable, and is useful in the detection of ''P.falciparum'' infection only.</br></br>At a high parasitaemia the sensitivity of HRP2 (like LDH-based tests) is likely to exceed 90% detection for ''P.falciparum''. At lower parasite levels (<1000 parasites/μL) the sensitivity will be significantly less but HP2-based assays may perform better than LDH-based assays in these circumstances.</br></br>HRP2 may be affected by false negative results when malaria antigen levels are very high (the prozone-like or postzone phenomenon (for full description in the RDT-interpretation sections).</br></br>''HRP2'' gene is increasingly subject to gene deletion in some geographical areas* which may cause false negative results (see sections on RDT interpretation).</span>
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!colspan="1" style = "background:#e1f1fd; border:solid; border-width: 3px;"|<span style="font-size:90%">''' ''P.falciparum'''</br>
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!colspan="1" style = "background:white; border:solid; border-width: 1px; color:black"|<span style="font-size:90%">At high parasitaemia expect high sensitivity (90-95%). This declines when parasite levels are lower (45-70%)
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!colspan="1" style = "background:#e1f1fd; border:solid; border-width: 3px;"|<span style="font-size:90%;">''' ''P.vivax'' '''</span></br>
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!colspan="1" style = "background:white; border:solid; border-width: 1px; color:black"|<span style="font-size:90%">Expect moderate to high sensitivity at high parasitaemia (70-90%). This declines markedly when parasite levels are lower (30-60%)
|-
!colspan="1" style = "background:#e1f1fd; border:solid; border-width: 3px;"|<span style="font-size:90%;">''' ''P.ovale & P.malarae'' '''</span></br>
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!colspan="1" style = "background:white; border:solid; border-width: 1px; color:black"|<span style="font-size:90%">Generally sensitivity is poor (approximately half the sensitivity shown for ''P.vivax'')
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!colspan="1" style = "background:#e1f1fd; border:solid; border-width: 3px;"|<span style="font-size:90%;">''' ''P.knowlesi'' '''</span></br>
|-
!colspan="1" style = "background:white; border:solid; border-width: 1px; color:black"|<span style="font-size:90%">Reports suggest variable sensitivity that may depend on test used, RDTs are reported tp detect this species well when parasitaemia is high.
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|colspan="1" style = "font-size:90%; color:black|<span style="color:black>[[RDT_Quiz_A_Q2|Quiz completed - go to finish)]]</span>
|colspan="1" style = "font-size:90%; color:black|<span style="color:black>[[RDT_Quiz_A_Summary|NEXT PAGE]]</span>

Latest revision as of 18:25, 2 December 2024

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RDT Quiz A Q5


RDT tests use specific antibodies to identify the malaria species. Users often believe that it is not important to know which antibodies their own test uses. However, different antibodies are known to have particular strengths and weaknesses.

  • Image from section "How RDT tests work"

    Image from section "How RDT tests work"

RDT tests that use antibodies that detect the malarial antigen HRP2 are widely used. Which of the statements below are true of HRP2 (select all that apply)?

The antigen identifies only P.falciparum
The antigen identifies P.vivax
HRP2 gene-deletion may affect results
Antibodies to pfLDH are more sensitive
May be negative in severe infection


Explanation of correct answer (click "Expand").
Short answer taken from section "RDT test antigens" (see the section for full details and links).

P.falciparum parasites produce “histidine-rich” proteins (HRP). The HRP2 antigen is highly expressed and stable, and is useful in the detection of P.falciparum infection only.

At a high parasitaemia the sensitivity of HRP2 (like LDH-based tests) is likely to exceed 90% detection for P.falciparum. At lower parasite levels (<1000 parasites/μL) the sensitivity will be significantly less but HP2-based assays may perform better than LDH-based assays in these circumstances.

HRP2 may be affected by false negative results when malaria antigen levels are very high (the prozone-like or postzone phenomenon (for full description in the RDT-interpretation sections).

HRP2 gene is increasingly subject to gene deletion in some geographical areas* which may cause false negative results (see sections on RDT interpretation).

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