What tests should be run for a patient recently diagnosed with HIV (Human Immunodeficiency Virus) Antigen antibody positive, with a history of hospital-acquired infections such as pneumonia and sepsis, and multi-drug resistant infections?

Initial Laboratory and Diagnostic Workup for Newly Diagnosed HIV-Positive Patients

All newly diagnosed HIV-positive patients require immediate CD4+ T-lymphocyte count and HIV viral load testing to determine disease stage, guide prophylaxis decisions, and assess treatment urgency. 1

Immediate Essential Tests

HIV-Specific Baseline Assessment

• CD4+ T-lymphocyte count – This is the single most critical test as it determines risk stratification for opportunistic infections and guides all subsequent management decisions 2, 1
• HIV viral load (plasma RNA quantification) – Essential for assessing disease severity and monitoring treatment response 1
• HIV resistance testing (genotypic) – Should be performed before initiating antiretroviral therapy to guide optimal drug selection 2

Baseline Laboratory Panel

• Complete blood count with differential and platelet count – Evaluates for cytopenias that may indicate advanced disease or opportunistic infections 1
• Comprehensive metabolic panel (electrolytes, renal function, liver function tests, glucose) – Establishes baseline organ function before initiating antiretroviral therapy 1

Infection Screening Based on CD4 Count

For patients with CD4+ count <200 cells/μL OR those with CD4+ >200 cells/μL but presenting with unexplained fever, weight loss, or thrush:

• Tuberculosis screening – Obtain three sputum specimens for acid-fast bacilli smear and culture, as TB is the leading cause of death in HIV-infected persons worldwide 2, 1
• Serum cryptococcal antigen (CrAg) – Critical screening test as cryptococcal meningitis carries grave prognosis and requires specific management before starting antiretroviral therapy 2, 1
• Chest radiograph – Essential for evaluating respiratory symptoms and detecting subclinical pneumonia or tuberculosis 1, 3
• Blood cultures (two sets) – HIV-infected patients have significantly increased incidence of bacteremia, especially at low CD4 counts 2, 4

For patients with CD4+ count >200 cells/μL without systemic symptoms:

• Opportunistic infection screening is generally not required unless specific clinical indicators are present 2

Additional Screening Tests

Sexually Transmitted Infections

• Syphilis serology (RPR or VDRL with confirmatory treponemal testing if positive) 2
• Hepatitis B surface antigen, surface antibody, and core antibody – Determines need for vaccination or treatment 2
• Hepatitis C antibody with reflex RNA testing if positive 2

Baseline Immunization Status

• Toxoplasma IgG serology – Identifies patients requiring prophylaxis when CD4 count drops below 100 cells/μL 2

Context-Specific Testing for Patients with Hospital-Acquired Infections

Given this patient's history of pneumonia, sepsis, and multi-drug resistant infections:

Respiratory Evaluation

• Sputum Gram stain and culture – Obtain before antibiotic initiation if patient can produce adequate specimen 2
• Sputum fungal culture – For any HIV-infected patient with pneumonia and CD4+ <200 cells/μL 2
• Blood fungal culture – Same indication as above 2
• Urinary antigen testing for Streptococcus pneumoniae and Legionella – Rapid diagnostic tools with high specificity, particularly valuable given increased incidence of bacteremic pneumococcal disease in HIV 2, 5

If Severe Illness Present (Fever, Dyspnea, or Significant Weight Loss)

• Bronchoscopy with bronchoalveolar lavage (BAL) – Should be strongly considered when: patients cannot produce adequate sputum, opportunistic infections are suspected, or pneumonia fails to respond to empiric therapy 2, 3
• CT chest – More sensitive than plain radiography for detecting small nodular or cavitary lesions characteristic of opportunistic pathogens 3

Critical Timing Considerations

Do not delay treatment while awaiting complete diagnostic workup. The presence of fever, weight loss, or dyspnea warrants urgent referral and empiric therapy 1. However, there is one critical exception: if cryptococcal meningitis is suspected or diagnosed, delay antiretroviral therapy initiation as immune reconstitution inflammatory syndrome can be fatal in this setting 1.

Common Pitfalls to Avoid

• Never assume normal chest radiograph excludes opportunistic infections – CT scanning should be obtained when CD4+ count is <200 cells/μL and clinical suspicion remains high despite negative plain films 3
• Do not use fluoroquinolone monotherapy without ruling out tuberculosis – This can mask TB symptoms, delay diagnosis, and promote resistance 1, 4
• Avoid macrolide monotherapy for bacterial pneumonia – HIV patients have increased risk of drug-resistant Streptococcus pneumoniae 4
• Obtain blood cultures before antibiotics – The yield is approximately 11% in community-acquired pneumonia and significantly higher in HIV-infected patients with bacteremia 2

Prophylaxis Initiation

Once CD4 count results are available and <200 cells/mm³, immediately initiate prophylaxis against Pneumocystis pneumonia (typically trimethoprim-sulfamethoxazole) and other opportunistic infections per established guidelines 1.