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== Standard aids diagnosis ==
== Standard aids diagnosis ==


A single multi-test algorithm is used to diagnose [[HIV|human immunodeficiency virus (HIV)]] infection causing acquired [[AIDS|immune deficiency syndrome (AIDS)]]. The basis is an [[ELISA]] (Enzyme-linked Immunosorbent Assay) test supplemented by [[Southern blotting#Western blot protein analysis|western blot]]. V případě problémů s diagnostikou či s pacientem je připravena celá škála dalších testů, které pomohou infekci HIV potvrdit či vyvrátit. In case of problems with the diagnosis or with the patient, a whole range of other tests is prepared to help confirm or refute the HIV infection.
A single multi-test algorithm is used to diagnose [[HIV|human immunodeficiency virus (HIV)]] infection causing acquired [[AIDS|immune deficiency syndrome (AIDS)]]. The basis is an [[ELISA]] (Enzyme-linked Immunosorbent Assay) test supplemented by [[Southern blotting#Western blot protein analysis|western blot]]. In case of problems with the diagnosis or with the patient, a whole range of other tests is prepared to help confirm or refute the HIV infection. In case of problems with the diagnosis or with the patient, a whole range of other tests is prepared to help confirm or refute the HIV infection.
 
[[File:Postup diagnostiky AIDS.png|náhled|Obr. 1: Doporučený postup při diagnostice HIV.]]
 
=== ELISA test ===
=== ELISA test ===
The basis of testing for the presence of HIV in the body is the detection of [[antibody|antibodies]] in serum or other body fluids. ELISA is one of the methods for detecting the patient's production of antibodies to the virus. The specificity and sensitivity of this test is more than 99%. Therefore, the ELISA is used in most cases as the first test in case of suspected HIV infection.
The basis of testing for the presence of HIV in the body is the detection of [[antibody|antibodies]] in serum or other body fluids. ELISA is one of the methods for detecting the patient's production of antibodies to the virus. The specificity and sensitivity of this test is more than 99%. Therefore, the ELISA is used in most cases as the first test in case of suspected HIV infection.


V případě, že je výsledek testu '''negativní''', není žádný důvod pro podezření na infekci HIV a pacient je považován za zdravého. Může ovšem nastat situace, kdy pacient byl infikován v nedávné době, čímž se ocitl v tzv. ''window period'' (diagnostickém okně). Infekce sice v organismu přítomná je, ale ještě se nezačaly vytvářet protilátky v detekovatelném množství. Diagnostické okno může trvat až 12 týdnů (podle typu ELISA). Falešně negativní může být ELISA i v případech [[autoimunní onemocnění|autoimunního onemocnění]], [[Renální selhání|ledvinného selhání]], [[hemodialýza|hemodialýzy]], [[cystická fibróza|cystické fibrózy]], vícečetného těhotenství či transfúzí a jaterních onemocnění.
If the test is '''negative''', there is no reason to suspect HIV infection and the patient is considered healthy. However, there may be situations where the patient has recently become infected, resulting in a ''window period''. Although the infection is present in the body, detectable amounts of antibodies have not yet begun to form. The diagnostic window can last up to 12 weeks (depending on the ELISA type). The ELISA may also be false negative in cases of [[autoimmune disease|autoimmune disease]], [[Renal failure|renal failure]], [[hemodialysis|hemodialysis]], [[cystic fibrosis|cystic fibrosis]], multiple pregnancies or transfusions, and liver disease.


Pokud se test ukáže '''pozitivní''', ELISA se opakuje, protože samozřejmě může docházet k falešné pozitivitě testu. Příčiny jsou stejné jako u falešné negativity testu, navíc lze dojít k falešně pozitivním výsledkům i při intravenózní aplikaci návykových látek, očkování ([[hepatitida]], [[vzteklina]],…) nebo [[Aktivní imunizace|vakcinaci]] proti HIV v rámci výzkumu. Je-li druhý ELISA test opět pozitivní, přistupuje se k dalšímu testování (western blot) pro vysokou pravděpodobnost přítomnosti infekce. Když jsou výsledky obou testů rozdílné (pozitivní a negativní), testuje se ještě jednou. Výhodné je provádět testy se vzorky odebranými stejnou metodou a vyhodnocené ve stejné laboratoři.
If the test is '''positive''', the ELISA is repeated because, of course, the test may be false-positive. The causes are the same as for a false-negative test, and false-positive results can also be obtained with intravenous drug use, vaccination ([[hepatitis]], [[rabies]],…) or [[HIV vaccination|HIV vaccination]] as part of the research. If the second ELISA test is positive again, further testing (western blot) is performed for a high probability of infection. If the results of both tests are different (positive and negative), it is tested again. It is advantageous to perform tests with samples taken by the same method and evaluated in the same laboratory.


=== Western blot ===
=== Western blot ===
[[Southernův blotting#Analýza proteinů westernovým přenosem|Western blot]] detekuje přítomnost protilátek proti proteinům [[vir]]u: core-proteiny (p17, p24, p55), polymerázy (p31, p51, p66) a envelope-proteiny (gp41, gp120, gp160). Hodnotí se vždy přítomnost určitých skupin protilátek. Pokud jsou přítomny jen některé protilátky, které nevyhovují kritériím pozitivního testu, je výsledek testu označen jako neurčitý.
[[Souther blotting#Western blot protein analysis|Western blot]] detects the presence of antibodies against [[virus]] proteins: core-proteins (p17, p24, p55), polymerases (p31, p51, p66) a envelope-proteins (gp41, gp120, gp160). The presence of certain groups of antibodies is always evaluated. If only some antibodies are present that do not meet the criteria of the positive test, the test result is marked as indeterminate.


'''Pozitivní výsledek''' western blotu v kombinaci s pozitivním [[ELISA]] testem již znamená téměř jistou přítomnost [[HIV]], pacient je HIV pozitivní a může být zahájena [[léčba]]. Specifita western blotu je 97,8 %, což ale znamená, že více než 2 % testů jsou falešně pozitivní. Chyba může být způsobena záměnou vzorků, kontaminací negativních vzorků pozitivními vzorky nebo protilátkami proti [[Hlavní histokompatibilitní komplex|HLA antigenům]] v lyzátu virů používaném při testu a chybnou interpretací elektroforetických proužků ze vzorku.
'''A positive''' Western blot in combination with a positive [[ELISA]] test already means the almost certain presence of [[HIV]], the patient is HIV positive and [[treatment ]]can start. The specificity of the western blot is 97.8%, which means that more than 2% of the tests are false positive. The error may be due to sample swapping, contamination of negative samples with positive samples, or antibodies to [[major histocompatibility complex|HLA antigenům]] antigens in the virus lysate used in the assay, and misinterpretation of electrophoretic bands from the sample.


'''Výsledek negativní''' je hodnocen jako nepřítomnost [[infekce]] a pacient je tudíž HIV negativní. U pacientů s vysokým rizikem nákazy se ovšem doporučuje opakované testování, neboť stejně jako u [[ELISA]] testu může být pacient infikován nedávno a testován zrovna v diagnostickém okénku.
'''A negative result''' is considered to be no [[infection]] and the patient is, therefore, HIV negative. However, re-testing is recommended for patients at high risk of infection, as with the [[ELISA]] the patient may be infected recently and tested in the diagnostic window.


'''Neurčitý výsledek''' může mít mnoho příčin. Testování v diagnostickém okénku způsobí, že některé [[protilátky]] nejsou ve vzorku přítomny v detekovatelném množství. Provedení testu v pozdní fázi infekce HIV může mít za následek nezachycení protilátek proti core-proteinům viru. Někteří zdraví lidé mohou bez zřejmého důvodu vytvářet protilátky, které vykazují zkříženou reakci se specifickými HIV-1 peptidy nebo rekombinantními [[antigeny]].
'''The indeterminate result''' can have many causes. Testing in the diagnostic window will cause some [[antibodies]] to be not detectable in the sample. Performing a test in the late phase of HIV infection may result in failure to capture antibodies to the virus's core proteins. Some healthy people may produce antibodies that cross-react with specific HIV-1 peptides or recombinant [[antigens]] for no apparent reason.


Jedná-li se o pacienta s vysokým rizikem nákazy HIV, doporučuje se sledovat jej alespoň po dobu 6 měsíců. U klientů s nízkou pravděpodobností infekce můžeme považovat test za negativní, ovšem také s možností dalšího sledování. V případě neurčitého výsledku western blotu je na řadě test množství virové [[RNA]] přítomné v plazmě: Plasma Viral Load.
If the patient is at high risk for HIV infection, it is recommended that they be monitored for at least 6 months. For clients with a low probability of infection, we can consider the test as negative, but also with the possibility of further monitoring. In the case of an indeterminate western blot result, it is time to test the amount of viral [[RNA]] present in the plasma: Plasma Viral Load.


=== Plasma Viral Load ===
=== Plasma Viral Load ===
Plasma Viral Load je komplex testů zjišťujících kvantitativně přítomnost virové RNA v plazmě pacienta. Skládá se ze tří částí:
[[File:Hiv-timecourse copy.svg|thumb|Graph showing HIV copies and CD4 counts in a human over the course of a treatment-naive HIV infection]]
Plasma Viral Load is a set of tests that quantitatively detect the presence of viral RNA in a patient's plasma. It consists of three parts:


* '''[[Polymerázová řetězová reakce|PCR]] assay''' – Polymerase Chain Reaction Assay;
* '''[[Polymerase Chain Reaction|PCR]] assay''' – Polymerase Chain Reaction Assay;
* '''[[DNA (nukleová kyselina)|bDNA]] assay''' – Branched-DNA Assay;
* '''[[DNA (nucleic acid)|bDNA]] assay''' – Branched-DNA Assay;
* '''NASBA''' – Nucleic Acid Sequence-Based Amplification.
* '''NASBA''' – Nucleic Acid Sequence-Based Amplification.


Nejčastějšími důvody pro Plasma Viral Load (PVL) jsou:
The most common reasons for Plasma Viral Load (PVL) are:
* v [[anamnéza|anamnéze]] je důvodné podezření pro nákazu [[HIV]], nebo pacient udává příznaky svědčící pro virovou infekci;
* there is a reasonable suspicion of [[HIV]], infection or the patient is showing signs of a viral infection;
* neurčité výsledky testů na [[HIV protilátky]] u pacienta s vysokým rizikem nákazy;
* vague [[HIV antibody]] test results in a patient at high risk of infection;
* potvrzení nově diagnostikované infekce HIV;
* confirmation of a newly diagnosed HIV infection;
* pozorování pacientů bez antivirové léčby;
* observation of patients without antiviral treatment;
* test před nasazením nebo změnou antivirové léčby;
* a test before starting or changing antiviral treatment;
* testování během léčby pro porovnání výsledků.
* testing during treatment to compare results.


[[Soubor:Hiv-timecourse.png|náhled|Obr. 2: Vývoj výsledků testů během infekce HIV.]]


Na obrázku č. 2 lze vidět vývoj výsledků testů PVL. Během diagnostického okénka [[ELISA]] a [[Southernův blotting#Analýza proteinů westernovým přenosem|western blotu]], kdy ještě nejsou vytvořeny [[protilátky]], lze zachytit určité množství virové RNA v plazmě. Limit citlivosti se může pohybovat až na úrovni 20–50 molekul RNA v mililitru plazmy. PVL test se ovšem jako počáteční užívá jen výjimečně, protože jeho cena je mnohem vyšší, než u ostatních standardních testů.
During the [[ELISA]] a [[Southern blotting#Western blot protein analysis|western blot]], diagnostic window, when [[antibodies]], have not yet formed, a certain amount of viral RNA can be captured in the plasma. The sensitivity limit can be as high as 20-50 RNA molecules per millilitre of plasma. However, the PVL test is used as an initial one only rarely, because its price is much higher than for other standardized tests.


Pro zjištění stupně nemoci se zjišťuje také počet [[T-lymfocyty|CD4+ T-lymfocytů]] v krvi, nejčastěji pomocí [[průtoková cytometrie|průtokové cytometrie]]. Toto vyšetření slouží i ke kontrole účinků antiretrovirální léčby. Nové testy ukazují, že v oblastech bez možnosti rychlého transportu chlazené a antikoagulované krve do laboratoře zřejmě bude možno pro sčítání CD4+ buněk a Plasma Viral Load použít vysušené krevní nátěry zpracované pomocí [[EIA (Enzyme Immunoassay)]].
To determine the degree of the disease, the number of [[T-lymphocytes|CD4+ T-lymphocytes]] in the blood is also determined, most often by [[flow cytometry|flow cytometry]]. This examination also serves to control the effects of antiretroviral treatment. New tests show that in areas without the possibility of rapid transport of chilled and anticoagulated blood to the laboratory, it will probably be possible to use dried blood smears treated with EIA  [[EIA (Enzyme Immunoassay)]] for CD4 + cell counting and Plasma Viral Load.


== Nové metody detekce HIV ==
== New methods of HIV detection ==


Podle studií provedených v roce 1995 v USA se zhruba 25% HIV pozitivních a 33% HIV negativních klientů nedostavila po testech na HIV pro své výsledky. Problém se netýká jen rozvinutých zemí. V rozvojových zemích existuje ztížená možnost laboratorního testování – správný a rychlý transport vzorků, nedostatek vybavení, apod. Bylo tedy nutno zajistit rychlé, pohodlné, levné a přitom spolehlivé metody, jak realizovat HIV testování.
According to studies conducted in 1995 in the USA, about 25% of HIV-positive and 33% of HIV-negative clients did not show up for HIV results after HIV testing. The problem is not just developed countries. In developing countries, there is a difficult possibility of laboratory testing - correct and fast transport of samples, lack of equipment, etc. It was, therefore, necessary to ensure fast, convenient, cheap and yet reliable methods to implement HIV testing.


=== Rychlé testování ===
=== Fast testing ===
Rychlé testy mohou být hotovy již během 30 minut. Zahrnují test na HIV-1 a HIV-2 protilátky s použitím různých nosičů (latexová aglutinace, immunoassay,…). Tyto testy se používají například v severoafrických zemích jakožto alternativa ELISA a western blotu. Rychlé testy mají specifitu více než 96% a senzitivitu okolo 99% při nízké ceně testování.
Quick tests can be completed in as little as 30 minutes. They include a test for HIV-1 and HIV-2 antibodies using various carriers (latex agglutination, immunoassay,…). These tests are used, for example, in North African countries as an alternative to ELISA and western blot. Rapid tests have a specificity of more than 96% and a sensitivity of about 99% at a low testing cost.


=== Amplifikace RNA ===
=== RNA amplification ===
Tato metoda je v současnosti ve fázi výzkumů. Existuje několik různých komerčních testovacích sad, které jsou zkoušeny na dobrovolnících. Amplifikace virových nukleových kyselin umožňuje zkrátit diagnostické okno až na 8 dnů.
This method is currently in the research phase. There are several different commercial test kits that are tested on volunteers. Viral nucleic acid amplification allows the diagnostic window to be shortened to up to 8 days.


=== Domácí testovací sady ===
=== Home test kits ===
Domácí testovací sady umožňují jednoduše odebrat vzorek krve a speciální filtrační papírek se vzorkem označeným pouze anonymním číslem odeslat do laboratoře. Klient je s výsledkem obeznámen telefonicky a je mu poskytnuta základní konzultace spolu s doporučením dalšího postupu.
Home test kits allow you to easily take a blood sample and send a special filter paper with a sample marked only with an anonymous number to the laboratory. The client is informed of the result by telephone and is provided with a basic consultation together with recommendations for further action.


=== Neinvazivní testy ===
=== Non-invasive tests ===
Neinvazivní testy zahrnují odběr transsudátu z ústní sliznice, moči a vaginálního sekretu. Pro analýzu vzorků se používá ELISA. Schopnost detekce je samozřejmě nižší, než u klasických metod, ovšem mezi výhody neinvazivního testování patří pohodlnost pro pacienta a také menší riziko komplikací pro pacienta i pro zdravotníka. Zmíněné tělní tekutiny obsahují [[IgG]] protilátky, které lze pomocí ELISA testu detekovat.
Non-invasive tests include the collection of transudate from the oral mucosa, urine and vaginal secretions. ELISA is used for sample analysis. The detection capability is, of course, lower than with conventional methods, but the advantages of non-invasive testing include patient comfort and also a lower risk of complications for both the patient and the healthcare professional. Said body fluids contain [[IgG]] antibodies which can be detected by an ELISA test.


== Vyšetření HIV u dárců krve ==
== HIV testing in blood donors ==
Vyšetření HIV se netýká jen pacientů, nýbrž i dárců krve. V České republice se podle vyhlášky o lidské krvi 143/2008 Sb. při každém odběru krve musí provést vyšetření diagnostických vzorků na přítomnost infekce HIV-1 a HIV-2 metodou stanovení protilátek a [[antigen]]u p24. Tím se minimalizuje riziko přenosu HIV z infikovaného dárce krve na příjemce.
HIV testing is not just about patients, but also about blood donors. In the Czech Republic, according to the Decree on Human Blood 143/2008 Coll. each blood sample must be tested for HIV-1 and HIV-2 infection by [[antibody]] and p24 antigen. This minimizes the risk of HIV transmission from the infected blood donor to the recipient.


<noinclude>
<noinclude>
== Odkazy ==
 
=== Související články ===
== References ==
=== Related articles ===
* [[HIV]]
* [[HIV]]
* [[AIDS]]
* [[AIDS]]
* [[Epidemiologie AIDS]]
* [[Epidemiologie AIDS]]
=== Použitá literatura ===
=== References ===
* {{Citace
* {{Cite
|typ = článek
|type = article
|korporace =  
|corporation =  
|příjmení1 = Cheng
|surname1 = Cheng
|jméno1 = B.
|name1 = B.
|příjmení2 = Landay
|surname2 = Landay
|jméno2 = A.
|name2 = A.
|příjmení3 = Miller
|surname3 = Miller
|jméno3 = V
|name3 = V
|kolektiv =
|others = no
|článek = Research needs and challenges in the development of HIV diagnostic and treatment monitoring tests for use in resource-limited settings
|article = Research needs and challenges in the development of HIV diagnostic and treatment monitoring tests for use in resource-limited settings
|časopis = Current Opinion in HIV and AIDS
|journal = Current Opinion in HIV and AIDS
|rok = July 2008
|year = July 2008
|ročník =  
|the_year =  
|svazek = 3
|volume = 3
|číslo =  
|number =  
|strany = 495-503
|pages = 495-503
|issn = 1746-630X
|issn = 1746-630X
|url = http://ovidsp.tx.ovid.com/sp-3.5.1a/ovidweb.cgi?T=JS&PAGE=fulltext&D=ovft&AN=01222929-200807000-00014&NEWS=N&CSC=Y&CHANNEL=PubMed
|url = http://ovidsp.tx.ovid.com/sp-3.5.1a/ovidweb.cgi?T=JS&PAGE=fulltext&D=ovft&AN=01222929-200807000-00014&NEWS=N&CSC=Y&CHANNEL=PubMed
}}
}}
* {{Citace
* {{Cite
|typ = článek
|type = article
|korporace =  
|corporation =  
|příjmení1 = Mylonakis
|surname1 = Mylonakis
|jméno1 = E.
|name1 = E.
|příjmení2 = Paliou
|surname2 = Paliou
|jméno2 = M.
|name2 = M.
|příjmení3 = Lally
|surname3 = Lally
|jméno3 = M.
|name3 = M.
|kolektiv = ano
|others = yes
|článek = Laboratory testing for infection with the human immunodeficiency virus: established and novel approaches
|article = Laboratory testing for infection with the human immunodeficiency virus: established and novel approaches
|časopis = The American Journal of Medicine
|journal = The American Journal of Medicine
|rok = Nov 2000
|year = Nov 2000
|ročník =  
|the_year =  
|svazek = 109
|volume = 109
|číslo =  
|number =  
|strany = 568-576
|pages = 568-576
|issn = 0002-9343
|issn = 0002-9343
|url = http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TDC-41JKV3D-8&_user=1490772&_coverDate=11%2F30%2F2000&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000053052&_version=1&_urlVersion=0&_userid=1490772&md5=4ffa42c0a536d1329d5f61c401284f41
|url = http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TDC-41JKV3D-8&_user=1490772&_coverDate=11%2F30%2F2000&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000053052&_version=1&_urlVersion=0&_userid=1490772&md5=4ffa42c0a536d1329d5f61c401284f41
}}
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* {{Citace
* {{Cite
|typ = článek
|type = article
|korporace =  
|corporation =  
|příjmení1 = Mylonakis
|surname1 = Mylonakis
|jméno1 = E.
|name1 = E.
|příjmení2 = Paliou
|surname2 = Paliou
|jméno2 = M.
|name2 = M.
|příjmení3 = Rich
|surname3 = Rich
|jméno3 = J
|name3 = J
|kolektiv =
|others = no
|článek = Plasma Viral Load Testing in the Management of HIV Infection
|article = Plasma Viral Load Testing in the Management of HIV Infection
|časopis = American Family Physician
|journal = American Family Physician
|rok = Feb 2001
|year = Feb 2001
|ročník =  
|the_year =  
|svazek = 63
|volume = 63
|číslo =  
|number =  
|strany = 483-490
|pages = 483-490
|issn = 0002-838X
|issn = 0002-838X
|url = https://www.aafp.org/afp/2001/0201/p483.html
|url = https://www.aafp.org/afp/2001/0201/p483.html
}}
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* {{Citace
* {{Cite
|typ = článek
|type = article
|korporace =  
|corporation =  
|příjmení1 = Masopust
|surname1 = Masopust
|jméno1 = J.
|name1 = J.
|příjmení2 = Ročková
|surname2 = Ročková
|jméno2 = R
|name2 = R
|příjmení3 =
|surname3 =
|jméno3 =  
|name3 =  
|kolektiv =
|others = no
|článek = Význam rozšíření screeningového vyšetření HIV infekce u dárců krve a krevních složek v České republice
|article = Význam rozšíření screeningového vyšetření HIV infekce u dárců krve a krevních složek v České republice
|časopis = Transfuze a hematologie dnes
|journal = Transfuze a hematologie dnes
|rok = 2003
|year = 2003
|ročník =  
|the_year =  
|svazek = 2
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|number =  
|strany = 59-64
|pages = 59-64
|issn = -
|issn = -
|url =  
|url =  
Line 152: Line 150:
</noinclude>
</noinclude>


[[Category:Mikrobiologie]]
[[Category:Microbiology]]
[[Category:Viry]]
[[Category:Viruses]]
[[Category:Infekční lékařství]]
[[Category:Infectious medicine]]
[[Category:Epidemiologie]]
[[Category:Epidemiology]]

Latest revision as of 18:07, 31 December 2021

Standard aids diagnosis[edit | edit source]

A single multi-test algorithm is used to diagnose human immunodeficiency virus (HIV) infection causing acquired immune deficiency syndrome (AIDS). The basis is an ELISA (Enzyme-linked Immunosorbent Assay) test supplemented by western blot. In case of problems with the diagnosis or with the patient, a whole range of other tests is prepared to help confirm or refute the HIV infection. In case of problems with the diagnosis or with the patient, a whole range of other tests is prepared to help confirm or refute the HIV infection.

ELISA test[edit | edit source]

The basis of testing for the presence of HIV in the body is the detection of antibodies in serum or other body fluids. ELISA is one of the methods for detecting the patient's production of antibodies to the virus. The specificity and sensitivity of this test is more than 99%. Therefore, the ELISA is used in most cases as the first test in case of suspected HIV infection.

If the test is negative, there is no reason to suspect HIV infection and the patient is considered healthy. However, there may be situations where the patient has recently become infected, resulting in a window period. Although the infection is present in the body, detectable amounts of antibodies have not yet begun to form. The diagnostic window can last up to 12 weeks (depending on the ELISA type). The ELISA may also be false negative in cases of autoimmune disease, renal failure, hemodialysis, cystic fibrosis, multiple pregnancies or transfusions, and liver disease.

If the test is positive, the ELISA is repeated because, of course, the test may be false-positive. The causes are the same as for a false-negative test, and false-positive results can also be obtained with intravenous drug use, vaccination (hepatitis, rabies,…) or HIV vaccination as part of the research. If the second ELISA test is positive again, further testing (western blot) is performed for a high probability of infection. If the results of both tests are different (positive and negative), it is tested again. It is advantageous to perform tests with samples taken by the same method and evaluated in the same laboratory.

Western blot[edit | edit source]

Western blot detects the presence of antibodies against virus proteins: core-proteins (p17, p24, p55), polymerases (p31, p51, p66) a envelope-proteins (gp41, gp120, gp160). The presence of certain groups of antibodies is always evaluated. If only some antibodies are present that do not meet the criteria of the positive test, the test result is marked as indeterminate.

A positive Western blot in combination with a positive ELISA test already means the almost certain presence of HIV, the patient is HIV positive and treatment can start. The specificity of the western blot is 97.8%, which means that more than 2% of the tests are false positive. The error may be due to sample swapping, contamination of negative samples with positive samples, or antibodies to HLA antigenům antigens in the virus lysate used in the assay, and misinterpretation of electrophoretic bands from the sample.

A negative result is considered to be no infection and the patient is, therefore, HIV negative. However, re-testing is recommended for patients at high risk of infection, as with the ELISA the patient may be infected recently and tested in the diagnostic window.

The indeterminate result can have many causes. Testing in the diagnostic window will cause some antibodies to be not detectable in the sample. Performing a test in the late phase of HIV infection may result in failure to capture antibodies to the virus's core proteins. Some healthy people may produce antibodies that cross-react with specific HIV-1 peptides or recombinant antigens for no apparent reason.

If the patient is at high risk for HIV infection, it is recommended that they be monitored for at least 6 months. For clients with a low probability of infection, we can consider the test as negative, but also with the possibility of further monitoring. In the case of an indeterminate western blot result, it is time to test the amount of viral RNA present in the plasma: Plasma Viral Load.

Plasma Viral Load[edit | edit source]

Graph showing HIV copies and CD4 counts in a human over the course of a treatment-naive HIV infection

Plasma Viral Load is a set of tests that quantitatively detect the presence of viral RNA in a patient's plasma. It consists of three parts:

  • PCR assay – Polymerase Chain Reaction Assay;
  • bDNA assay – Branched-DNA Assay;
  • NASBA – Nucleic Acid Sequence-Based Amplification.

The most common reasons for Plasma Viral Load (PVL) are:

  • there is a reasonable suspicion of HIV, infection or the patient is showing signs of a viral infection;
  • vague HIV antibody test results in a patient at high risk of infection;
  • confirmation of a newly diagnosed HIV infection;
  • observation of patients without antiviral treatment;
  • a test before starting or changing antiviral treatment;
  • testing during treatment to compare results.


During the ELISA a western blot, diagnostic window, when antibodies, have not yet formed, a certain amount of viral RNA can be captured in the plasma. The sensitivity limit can be as high as 20-50 RNA molecules per millilitre of plasma. However, the PVL test is used as an initial one only rarely, because its price is much higher than for other standardized tests.

To determine the degree of the disease, the number of CD4+ T-lymphocytes in the blood is also determined, most often by flow cytometry. This examination also serves to control the effects of antiretroviral treatment. New tests show that in areas without the possibility of rapid transport of chilled and anticoagulated blood to the laboratory, it will probably be possible to use dried blood smears treated with EIA EIA (Enzyme Immunoassay) for CD4 + cell counting and Plasma Viral Load.

New methods of HIV detection[edit | edit source]

According to studies conducted in 1995 in the USA, about 25% of HIV-positive and 33% of HIV-negative clients did not show up for HIV results after HIV testing. The problem is not just developed countries. In developing countries, there is a difficult possibility of laboratory testing - correct and fast transport of samples, lack of equipment, etc. It was, therefore, necessary to ensure fast, convenient, cheap and yet reliable methods to implement HIV testing.

Fast testing[edit | edit source]

Quick tests can be completed in as little as 30 minutes. They include a test for HIV-1 and HIV-2 antibodies using various carriers (latex agglutination, immunoassay,…). These tests are used, for example, in North African countries as an alternative to ELISA and western blot. Rapid tests have a specificity of more than 96% and a sensitivity of about 99% at a low testing cost.

RNA amplification[edit | edit source]

This method is currently in the research phase. There are several different commercial test kits that are tested on volunteers. Viral nucleic acid amplification allows the diagnostic window to be shortened to up to 8 days.

Home test kits[edit | edit source]

Home test kits allow you to easily take a blood sample and send a special filter paper with a sample marked only with an anonymous number to the laboratory. The client is informed of the result by telephone and is provided with a basic consultation together with recommendations for further action.

Non-invasive tests[edit | edit source]

Non-invasive tests include the collection of transudate from the oral mucosa, urine and vaginal secretions. ELISA is used for sample analysis. The detection capability is, of course, lower than with conventional methods, but the advantages of non-invasive testing include patient comfort and also a lower risk of complications for both the patient and the healthcare professional. Said body fluids contain IgG antibodies which can be detected by an ELISA test.

HIV testing in blood donors[edit | edit source]

HIV testing is not just about patients, but also about blood donors. In the Czech Republic, according to the Decree on Human Blood 143/2008 Coll. each blood sample must be tested for HIV-1 and HIV-2 infection by antibody and p24 antigen. This minimizes the risk of HIV transmission from the infected blood donor to the recipient.


References[edit | edit source]

Related articles[edit | edit source]

References[edit | edit source]

  • MYLONAKIS, E. – PALIOU, M. – RICH, J. Plasma Viral Load Testing in the Management of HIV Infection. American Family Physician [online]. Feb 2001, vol. 63, p. 483-490, Available from <https://www.aafp.org/afp/2001/0201/p483.html>. ISSN 0002-838X. 
  • MASOPUST, J. – ROČKOVÁ, R. Význam rozšíření screeningového vyšetření HIV infekce u dárců krve a krevních složek v České republice. Transfuze a hematologie dnes. 2003, vol. 2, p. 59-64, 
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