| Angiography, magnetic resonance | 
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| Angiotensin | 
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| Ankle-brachial index (ABI) | 
| Anorectal infections, STIs | 
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| Anthrax | 
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| Antibody and peptide tumor imaging | 
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| Antibody screen, prenatal | 
| Antibody tests, viral | 
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| Antideoxyribonuclease-B titer | 
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| Antidiuretic hormone (ADH) suppression test, water-loading | 
| Anti-DNase-B | 
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