Diagnostic Tests

1. Overview: What this test reveals and why it is important Lactate dehydrogenase is a cytoplasmic enzyme found in nearly all cells of the body, with highest concentrations in heart, liver, skeletal muscle, kidney, red blood cells, and certain cancers. It catalyses the reversible conversion of lactate to pyruvate and is released into the bloodstream when cells are damaged or destroyed. Because it is so widely distributed, LDH is a sensitive but entirely non‑specific marker of

1. Overview: What this test reveals and why it is important C‑Reactive Protein is an acute‑phase protein synthesised by the liver in response to inflammation. It is one of the most sensitive and dynamic markers of systemic inflammation, rising within 4–6 hours of an inflammatory stimulus and doubling every 8 hours under continuous stimulation. Its half‑life is constant (~19 hours); therefore, the circulating level is determined entirely by the rate of production, which is dir

1. Overview: What this test reveals and why it is important Platelets (thrombocytes) are tiny, anucleate cell fragments produced by megakaryocytes in the bone marrow and released into the bloodstream. They are the first responders of haemostasis, aggregating at sites of vascular injury to form a temporary plug and releasing factors that activate the coagulation cascade. Beyond clotting, platelets participate in inflammation, immune modulation, wound healing, and even tumour b

1. Overview: What this test reveals and why it is important Plasma cells are terminally differentiated B‑lymphocytes responsible for producing immunoglobulins (antibodies). They normally reside in the bone marrow and lymphoid tissues; they are not present in the peripheral blood of healthy individuals. Detection of plasma cells on a blood smear or automated differential is always abnormal and requires immediate investigation. The plasma cell count is reported either as a perc

1. Overview: What this test reveals and why it is important Immature granulocytes are precursor white blood cells—specifically metamyelocytes, myelocytes, and promyelocytes—that are normally confined to the bone marrow. Their appearance in peripheral blood is always abnormal and indicates a left shift: an accelerated release of granulocytes from the marrow in response to significant demand. The immature granulocyte (IG) count includes both the percentage and absolute number o

1. Overview: What this test reveals and why it is important Nucleated red blood cells are erythrocyte precursors that normally reside exclusively in the bone marrow. Their presence in the peripheral blood of adults and older children is always pathological and represents an emergency signal of bone marrow stress, infiltration, or extramedullary haematopoiesis. In newborns, a small number of NRBCs is physiological during the first days of life, but persistence or elevation bey

1. Overview: What this test reveals and why it is important Eosinophils are a specialized subset of white blood cells that play a critical role in defending the body against parasitic infections and in modulating allergic and inflammatory responses. They are produced in the bone marrow, circulate briefly in the blood, and then migrate into tissues—particularly the gastrointestinal tract, respiratory epithelium, skin, and genitourinary tract—where they reside and exert their e

1. Overview: What this test reveals and why it is important Basophils are the rarest granulocytes, representing less than 1% of peripheral blood leukocytes. For more than a century after their discovery, their roles remained enigmatic due to their scarcity and similarity to tissue‑resident mast cells . Today, basophils are recognised as critical effector cells in type 2 immune responses, including chronic allergic inflammation, protective immunity against parasites, and emerg

1. Overview: What this test reveals and why it is important Monocytes are the largest white blood cells and a critical component of the innate immune system. They originate in the bone marrow, circulate in the blood for 1–3 days, then migrate into tissues where they differentiate into macrophages or dendritic cells. These tissue‑resident cells are essential for phagocytosis of pathogens and cellular debris, antigen presentation to lymphocytes, and orchestration of inflammator

1. Overview: What this test reveals and why it is important Neutrophils are the most abundant white blood cells and the body’s first line of defence against bacterial and fungal infections. They are produced in the bone marrow and circulate in the blood, ready to migrate to sites of infection or tissue injury. The absolute neutrophil count (ANC) is the actual number of neutrophils per volume of blood. It is calculated from the total white blood cell count and the percentage o

1. Overview: What this test reveals and why it is important Lymphocytes are the second most abundant white blood cells and the cornerstone of adaptive immunity. They comprise three main functional subsets: · T lymphocytes (T cells) – cell‑mediated immunity; helper, cytotoxic, and regulatory subsets. · B lymphocytes (B cells) – humoral immunity; differentiate into plasma cells to produce antibodies. · Natural killer (NK) cells – innate lymphoid cells; kill virally infected and

1. Overview: What this test reveals and why it is important Neutrophils are the most abundant white blood cells and the body’s first line of defence against bacterial and fungal infections. They are produced in the bone marrow and circulate in the blood, ready to migrate to sites of infection or tissue injury. The absolute neutrophil count (ANC) is the actual number of neutrophils per volume of blood. It is calculated from the total white blood cell count and the percentage o

1. Overview: What this test reveals and why it is important The APO B / APO A1 ratio is one of the most powerful predictors of atherosclerotic cardiovascular disease risk. It captures the balance between pro‑atherogenic and anti‑atherogenic lipoprotein particles. · Apolipoprotein B (APO B) is the primary structural protein found in very low‑density lipoprotein (VLDL), intermediate‑density lipoprotein (IDL), low‑density lipoprotein (LDL), and lipoprotein(a). Each atherogenic p

1. Overview: What this test reveals and why it is important Apolipoprotein B is the primary structural protein found in all atherogenic lipoproteins – very low‑density lipoprotein (VLDL), intermediate‑density lipoprotein (IDL), low‑density lipoprotein (LDL), and lipoprotein(a). Unlike LDL cholesterol, which estimates the cholesterol content within these particles, Apo‑B measures the number of these potentially harmful particles. Each VLDL, IDL, LDL, and Lp(a) particle contain

1. Overview: What this test reveals and why it is important Hemoglobin is the iron‑containing protein within red blood cells that carries oxygen from the lungs to the tissues and returns carbon dioxide for exhalation. It is the primary measure of the blood's oxygen‑carrying capacity. Hemoglobin concentration is the most reliable indicator of anaemia (too low) or polycythaemia (too high). Unlike haematocrit or red blood cell count, hemoglobin directly measures the oxygen‑carry

1. Overview: What this test reveals and why it is important Apolipoprotein A-I is the primary structural protein component of high‑density lipoprotein (HDL), often called "good cholesterol." It is synthesised in the liver and intestine and plays a critical role in reverse cholesterol transport – the process of removing excess cholesterol from arterial walls and transporting it back to the liver for excretion. Beyond cholesterol efflux, Apo-A1 possesses anti‑inflammatory, anti

1. Overview: What this test reveals and why it is important Lipoprotein (a) – abbreviated Lp(a) – is a low‑density lipoprotein (LDL) particle to which a second protein, apolipoprotein(a), is covalently attached. This unique structure makes Lp(a) both pro‑atherogenic and pro‑thrombotic. Unlike LDL cholesterol, Lp(a) levels are 80–90% genetically determined and remain remarkably stable throughout life, influenced little by diet, exercise, or most standard lipid‑lowering therapi

1. Overview: What this test reveals and why it is important Immunoglobulin A (IgA) is the dominant antibody class on mucosal surfaces—respiratory, gastrointestinal, and genitourinary tracts—and in secretions such as saliva, tears, and breast milk. It exists primarily as a dimer linked by a J chain and secretory component, which protects it from proteolytic degradation. IgA serves as the immune system's frontline defence, neutralising pathogens before they invade deeper tissue

1. Overview: What this test reveals and why it is important Immunoglobulin M (IgM) is the largest antibody in the human circulatory system and the first to be produced during an initial (primary) immune response. It is synthesised by plasma cells upon first exposure to an antigen and appears within days, before IgG. IgM is also the main immunoglobulin expressed on naïve B cells. In blood, it circulates as a pentamer, giving it high avidity for pathogens. Natural antibodies—su

1. Overview: What this test reveals and why it is important Immunoglobulin G (IgG) is the most abundant antibody class in human blood, constituting approximately 75–80% of circulating immunoglobulins. It is the cornerstone of long‑term humoral immunity. IgG is produced by plasma cells in response to prior infection or vaccination, providing durable protection against bacteria, viruses, and toxins. It crosses the placenta, conferring passive immunity to the newborn. Total IgG