Diagnosing HIV and AIDS is a systematic process that combines clinical assessment, laboratory testing, and long-term follow-up. Physicians utilize detailed medical histories, symptom analysis, and multi-stage biological testing to confirm whether a patient is infected with the human immunodeficiency virus (HIV) and to assess the stage of the disease. Early diagnosis not only enables prompt initiation of antiretroviral therapy but also effectively blocks virus transmission. Therefore, the medical community emphasizes the importance of proactive screening and regular monitoring.
The diagnostic process typically involves three stages: initial screening, confirmatory testing, and disease staging assessment. Screening may be performed via blood, saliva, or home test kits, while confirmatory tests require laboratory techniques such as Western blot or nucleic acid amplification tests (NAAT). AIDS diagnosis further involves evaluating CD4+ T cell counts, viral load, and the presence of specific complications to determine the extent of immune system damage. The following provides a detailed explanation of each diagnostic step and key techniques.
Clinical assessment is the foundation of diagnosis. Physicians first inquire about exposure risks and symptom history. Early HIV infection may present with flu-like symptoms such as fever, lymphadenopathy, or rash, but these non-specific signs cannot confirm diagnosis alone. Therefore, the evaluation should carefully explore the following key information:
During clinical assessment, physicians also evaluate the patient’s overall health status, including skin examination, lymph node palpation, and organ function assessment. For example, oral candidiasis or Pneumocystis pneumonia symptoms may suggest advanced AIDS.
Screening tests include antibody/antigen combination assays (such as fourth-generation ELISA) and nucleic acid amplification tests (NAT). Antibody/antigen tests detect viral protein p24 and antibodies, suitable for detecting infection within 2-6 weeks post-infection. NAT directly measures viral RNA, offering high sensitivity but at higher cost, often used as an initial screening tool for high-risk populations.
Saliva tests and home self-testing kits (such as rapid antibody tests) provide non-invasive options, but results from self-tests should be confirmed by healthcare professionals. For example, some self-testing tools may produce false negatives due to user error or early infection, necessitating blood tests for confirmation.
When screening results are positive, confirmatory tests are required to exclude false positives. Common methods include Western blot immunoassay or immunofluorescence assay (IFA), which differentiate specific antibody responses. For example, Western blot shows specific bands for gp41 or gp120 antigens, confirming infection.
Viral genotyping is used for resistance testing, especially in cases of treatment failure. It involves sequencing viral genes to identify mutations, helping to adjust medication regimens. Such tests are typically performed during initial treatment and ongoing monitoring.
Proactive screening is a key component of diagnosis. The U.S. Centers for Disease Control and Prevention (CDC) recommends that all adults aged 13-64 undergo at least one screening, with high-risk groups tested annually. Common clinical screening tools include:
Assessment tools also include the "clinical staging system," which classifies AIDS into stages 1 through 3 based on CD4+ T cell counts and specific complications. For example, Stage 3 indicates severe immunodeficiency, with common indicators including CD4+ cells below 200 cells/μL or the presence of AIDS-defining illnesses.
HIV symptoms can mimic other immune-related diseases. Differential diagnosis is necessary to exclude other possibilities:
In advanced AIDS, differentiation from malignancies (such as lymphoma), tuberculosis, or Pneumocystis pneumonia is essential. For instance, persistent dry cough and dyspnea require chest X-ray and biopsy to distinguish between pulmonary infection and malignancy.
Early diagnosis significantly improves prognosis. Antiretroviral therapy (ART) can reduce viral load to undetectable levels, allowing immune system recovery. According to WHO data, early treatment can reduce transmission risk by 95% and delay progression to AIDS.
For individuals, early diagnosis provides psychological and physiological support. Patients can receive counseling, nutritional support, and complication prevention early. For example, initiating treatment within three months of infection accelerates CD4+ T cell recovery by 2-3 times compared to late treatment. On a societal level, early diagnosis can interrupt transmission chains and reduce overall infection rates.
However, some patients delay seeking medical care due to fear or social stigma, leading to diagnosis at AIDS stage. Therefore, healthcare institutions often combine anonymous screening with mental health support to encourage testing among high-risk groups. For example, some countries offer free home testing kits linked to counseling hotlines.
Home or rapid screening tests for HIV antibodies have a sensitivity of about 99% and specificity exceeding 99.5%. However, positive results must be confirmed with laboratory tests such as Western blot or nucleic acid testing. It is recommended to test after the window period of approximately three months to ensure accuracy.
After starting antiretroviral therapy (ART), is it still necessary to regularly check CD4 counts and viral load?Yes. Even if viral load becomes undetectable, it is recommended to monitor CD4 counts and viral load every 3-6 months to assess immune recovery and detect drug resistance. If CD4 counts fall below 200/μL or viral load rebounds, treatment adjustments may be necessary.
For adolescents under 18 diagnosed with HIV, can they use adult medication dosages directly?It is not recommended to use adult dosages directly. Doses should be adjusted based on weight and developmental stage, and drugs with minimal impact on liver and kidney function should be chosen. According to guidelines, individuals over 12 years old may use standard adult regimens under regular evaluation of growth and development by an infectious disease specialist.
Within the 72-hour window for post-exposure prophylaxis (PEP), if the medication is missed, does the efficacy decrease significantly?If more than 24 hours have passed without taking the medication, the missed dose should be taken immediately. If close to the next scheduled dose, skip the missed dose rather than doubling up. Delayed medication reduces the chance of successful prevention. It is advised to set reminders every 4 hours and strictly adhere to the schedule.
Can HIV-infected individuals transmit the virus through daily contact such as sharing meals or shaking hands after effective treatment?No. Modern evidence confirms that when patients are on regular ART and have an undetectable viral load below 200 copies/mL, they are not infectious (U=U principle). The virus concentration in saliva, sweat, or urine is extremely low, and routine contact such as sharing utensils, kissing, or skin contact does not transmit HIV.
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