HumanImmunodeficiency Virus (HIV) Screening Test
Introductionto the problem
HIVscreening is the taking of human blood samples and testing it to seewhether it has antibodies that can react with HIV. Such tests arenormally very accurate to ensure that very efficient results areobtained from the blood samples collected so that the person underthe test will be offered appropriate counseling where necessary. Thisscreening will help people know whether they are infected with HIV atearly stages. In America, it is estimated that almost 1.2 millionpersons are infected with HIV, and approximately 50,000 are infectedannually. Studies show that it’s only about 20%-25% of the infectedpeople know their status while others don’t know whether they havethe infection. Every individual is at risk of contracting HIV, and noone is excluded from the screening exercise. It’s recommended thatat least every individual between 15-60 years should be screened toconfirm their status. Those who fall below the age of 15 years andabove 65 years can as well be screened if found that they are at riskof contracting the infection. Similarly, all pregnant women should bescreened to confirm their HIV status before they deliver to avoidinfecting the infants.
Descriptionof the screening test
Screentesting is entirely about testing the blood sample of a patient toconfirm whether he/she is infected with HIV or not. One method ofscreen test is the rapid test. Rapid test occurs where the bloodsamples are tested at the point where the blood has been obtained,and the victim is given answers within a very short time. Blood fromthe finger of the victim is typically used for the test. In case theresults indicate the absence of the infection the victim will beimmediately informed that he is negative. However if the resultsindicate the presence of HIV, further diagnosis will be taken forconfirmatory purposes. This is the final test that will be carried ina public health laboratory, and the results will be released afterone or two weeks.
Laboratorytesting of blood is carried out by trained individuals who do thetesting and the result so obtained is final. The results can then becommunicated to the clinical officer who was responsible for handlingthe victim or the one who is supposed to give back the report to thepatient.
HIVis a global pandemic. Worldwide, statistics carried out in the year2014 indicated that averagely 36.9 million people were infected withHIV. Out of this number, children accounted to about 2.6 millioncomprising a prevalence of about 0.8%. Of the total number infected,70% come from sub-Sahara Africa, and it’s only about 54% of themwho know about their HIV status. In the U.S.A, HIV is a nationaldisaster affecting every state. According to the statistics carriedout in the year 2013, 1.2 million people in the US were living withHIV. The adult prevalence was 0.4%-0.9%. The same year recorded newinfections of the HIV of about 50,000. Out of the infectedpopulation, one person in seven people did not know whether he/shehad the HIV. The southern states are the most affected with the virusin the US. The prevalence has also been observed to be higher amongthe men homosexuals but also, people of different races are affecteddifferently.
Thegold standard diagnostic test
Whenscreen testing results indicate that the person who gave the bloodsample has tested positive, this is not final to conclude thepresence of the virus. A further confirmatory test will have to becarried out to confirm the presence of the virus. The confirmatorytest gives surety that the screening was correctly done. If this testindicates the presence of the virus, the message is communicated tothe healthcare provider who as well communicates back to the personbelonging to the blood sample. At some cases, the confirmatory testmay not give the expected results. It may fail to identify thepresence or absence of the HIV or it may give a different resultcompared to the one provided by the screen test. In such a case wherethe results differ, further supplementary tests may be carried out inthe laboratory or the blood sample can as well be sent to a differentlaboratory for further testing to ascertain the results early onfound whether they are valid or not. The results that may be found atthis point will give the final test regarding the blood sample thatwas under the test.
Sensitivity,false positives, specificity, false negatives data and discussion ofinterpretation of results
Normally,HIV tests are very accurate when the tests have been correctlycarried out. To test the accuracy of the HIV tests, sensitivity andspecificity measures ought to be carried out. In sensitivity, it isexpected that there’s a likelihood of an HIV-positive persontesting positive after a test has been correctly carried out. If thesensitivity is lower, chances of false negatives are increased, thatis, a person is likely to test negative while in reality he/she ispositive. Specificity, on the other hand, is the probability that anHIV negative person will test negative after the tests have been doneto that person correctly. In application, lower specificity is anindication that false positives are increased, that is, one can testpositive while in reality the same person is HIV negative.
Inthe real life world, fourth-generation screen tests and other rapidtests are 99.9% sensitive. This means that if a sample of 1000 peoplewho are infected with the HIV is taken, the tests will confirm that999 are infected with the HIV while one of them may test negativeeven though he/she is positive. For such a test, if the highestnumbers of individuals being tested for the HIV are negative, thereis an extremely low likelihood of a negative result turning out to befalse (Wilton, 2015).
Onthe other hand, specificity of the HIV screen testes is 99.5%,meaning that they are slightly lower than sensitivity. Theinterpretation of this is that, if a sample of 1000 HIV positivepeople is taken for a test, there is a likelihood that 995 peoplewill test positive while 5 of them are likely to test incorrectlypositive. In this situation, the false positives may be extremelylow, but the probability will be higher though at a small margin thanthe false negatives. This gives the reason confirmatory tests arenecessary especially using the Western blot type of test which has aspecificity of 100% meaning that the chance of false-positive resultis zero.
Prosand cons of this screening test
Tostart with, the screen tests, especially the rapid tests, are veryfast, and the results are obtained almost immediately the bloodsample has been taken for a test. This reduces the anxiety and fearthat one may develop in the course of waiting for the results.Secondly, patients will know their HIV status as early as possibleand start medication early to ensure the victim leads a healthy life.People will, therefore, take initiatives to limit the spread of theSTIs once they have known their HIV status. Lastly, the screen testsare very accurate, and it’s the only sure way that one can be surewhether he is infected or not after appropriate tests have been done(Sax, Cohen and Kuritzkes, 2013).
Themain disadvantage with these screen tests is that the results are notreliable especially during the window period of the HIV infectionperiod and, therefore, cannot be regarded as the outcome until afterfurther confirmatory tests have been carried out on that blood sample(Taylor et al, 2015).
Costsand future predictions of the disease
Screentests are expensive than the conventional methods that areapplicable. Further tests will be more expensive compared to theprevious ones as the precise answer is required to determine thepresence or absence of the infection. However, when screen tests areperformed on a vast number of people, they are affordable.
Thequality of the display tests as far as HIV testing is concerned havebeen increasing over time. More advanced screen methods should bedeveloped that are reliable without further tests to confirm thepresence of the infection on people.
Instituteof Medicine (U.S.), & National Academies Press (U.S.). (2010).HIVScreening and Access to Care: Exploring Barriers and Facilitators toExpand HIV Testing.Washington, D.C: The National Academies Press.
PublicHealth Agency of Canada & Centre for Communicable Diseases andInfection Control (Canada). (2012). HumanImmunodeficiency Virus: HIV screening and testing guide.
Sax,E.P,. Cohen, J. C & Kuritzkes, D.R. (2013). HIV Essentials. Jones& Bartlett Publishers.
Taylor,D et al. (2015). Probability of a False-Negative HIV Antibody TestResult during the Window Period: a Tool for Pre and Post-testCounseling. InternationalJournal of STD & AIDS.Sage Publications.
Wilton,J. (2015). HIVTesting Technologies,retrieved fromhttp://www.catie.ca/en/fact-sheets/testing/hiv-testing-technologieson 3rdFebruary 2016