While Rheumatoid Factor is commonly tested, Anti-CCP antibodies are much more specific for Rheumatoid Arthritis and can often be detected earlier in the course of the disease compared to RF.

D-dimer is a fibrin degradation product. Because it is sensitive but not specific, a negative D-dimer test is highly useful for ruling out Pulmonary Embolism (PE) or DVT in patients with a low clinical probability.

The Urea Breath Test utilizes the fact that H. pylori produces the enzyme urease, which breaks down urea into ammonia and CO2. The patient swallows labeled urea, and the labeled CO2 is detected in the exhaled breath.

Modern 4th generation ELISA tests detect both HIV antibodies and the p24 antigen. It is the standard screening tool due to its high sensitivity; positive results are then confirmed with a Western Blot or differentiation assay.

The Papanicolaou (Pap) smear is a cytological screening test used to detect precancerous or cancerous changes in the cervix. It has significantly reduced cervical cancer mortality through early detection.

Serum Ferritin is the most sensitive and specific lab test for iron deficiency as it reflects total body iron stores. A low ferritin level is almost always diagnostic of iron deficiency, even before anemia develops.

In a symptomatic patient showing the classic '3 Ps' of diabetes (excessive urination, thirst, and hunger), a random blood glucose test of 200 mg/dL or higher is diagnostic for Diabetes Mellitus.

While Sputum Smear Microscopy is often the first step due to its speed, Sputum Culture remains the gold standard because it can detect low numbers of mycobacteria and allows for drug sensitivity testing, though it takes several weeks for results.

Lactase is produced in the small intestine. It breaks down the disaccharide lactose into the simple sugars glucose and galactose for absorption.

Lipase is secreted primarily by the pancreas and works in the small intestine to digest fats after they have been emulsified by bile.