An expression of the relation of one quantity to another (e.g., of a proportion or rate). See also index (2), quotient. [L. ratio (ration-) a reckoning, reason, fr. reor, pp. ratus, to reckon, compute]
absolute terminal innervation r. the number of motor endplates divided by the number of terminal axons related to them.
accommodative convergence-accommodation r. (AC/A) the amount of convergence (measured in prism diopters of convergence) divided by the amount of accommodation (measured in diopters) required to direct both eyes upon an object.
A/G r. abbreviation for albumin-globulin r.
albumin-globulin r. (A/G r.) the r. of albumin to globulin in the serum or in the urine in kidney disease; the normal r. in the serum is approximately 1.55.
ALT:AST r. the r. of serum alanine aminotransferase to serum aspartate aminotransferase; elevated serum levels of both enzymes characterize hepatic disease; when both levels are abnormally elevated and the ALT:AST r. is greater than 1.0, severe hepatic necrosis or alcoholic hepatic disease is likely; when the r. is less than 1.0, an acute non-alcoholic hepatic condition is favored.
amylase-creatinine clearance r. a test for the diagnosis of acute pancreatitis; it is determined by measuring amylase and creatinine in serum and urine in apparently healthy individuals the renal clearance of amylase is less than 5% that of creatinine; in acute pancreatitis the r. is said to be greater than 0.05 or 5%.
body-weight r. body weight (in grams) divided by stature (in centimeters).
cardiothoracic r. the r. of the horizontal diameter of the heart to the inner diameter of the rib cage at its widest point as determined on a chest roentgenogram.
case fatality r. the mortality rate of a disease, usually expressed per 100 cases.
r. of decayed and filled surfaces (RDFS) an index of decayed and filled permanent surfaces per person, per full complement of 122 tooth surfaces.
r. of decayed and filled teeth (RDFT) an index of decayed and filled permanent teeth per person, per full complement of 28 teeth.
extraction r. (E) the fraction of a substance removed from the blood flowing through the kidney; it is calculated from the formula (A -V)/A, where A and V, respectively, are the concentrations of the substance in arterial and renal venous plasma.
fertility r. A measure of the fertility of a population based on the female population in the child-bearing age-group, defined as ages 15-49 years.
flux r. the r. of the two unidirectional fluxes through a particular boundary layer or membrane.
functional terminal innervation r. the number of muscle fibers divided by the number of axons that innervate them.
grid r. in a radiographic scatter-absorbing grid, the r. of the height to the width of the gaps between lead strips; a higher grid r. removes more scattered radiation but requires more careful x-ray tube positioning to avoid grid cutoff of the primary radiation beam.
gyromagnetic r. in nuclear magnetic resonance, the r. of the magnetic dipole moment of the nucleus to the nuclear spin angular momentum; the gyromagnetic r. is a unique value for each type of nucleus.magnetogyric r;
hand r. the r. of the length of the hand (measured on the dorsum from the styloid process of the ulna to the tip of the third finger) to the width across the knuckles.
IRI/G r. the r. of immunoreactive insulin to serum or plasma glucose; in hypoglycemic states a r. of less than 0.3 is usual with the exception of the hypoglycemia due to insulinoma, where the r. is often higher than 0.3.
K:A r. abbreviation for ketogenic-antiketogenic r.
ketogenic-antiketogenic r. (K:A r.) the proportion between substances that form ketones in the body and those that form d-glucose.
lecithin/sphingomyelin r. (L/S r.) a r. used to determine fetal pulmonary maturity, found by testing the amniotic fluid; when the lungs are mature, lecithin exceeds sphingomyelin by 2 to 1.
L/S r. abbreviation for lecithin/sphingomyelin r.
magnetogyric r. (mag´ne-to-gy-rik) gyromagnetic r
mass-action r. the ratio of the product of all of the product concentrations divided by the product of all of the reactant concentrations of a particular reaction; when the reaction has been completed (i.e., t = infinite), then this r. is equal to the equilibrium constant.
M:E r. the r. of myeloid to erythroid precursors in bone marrow; normally it varies from 2:1 to 4:1; an increased r. is found in infections, chronic myelogenous leukemia, or erythroid hypoplasia; a decreased r. may mean a depression of leukopoiesis or normoblastic hyperplasia depending on the overall cellularity of the bone marrow.
mendelian r. the r. of progeny with a particular phenotypes or genotypes expected in accordance with Mendel's law among the offspring of matings specified as to genotype or phenotype.
molecular weight r. (Mr) molecular weight
nuclear-cytoplasmic r. r. of volume of nucleus to volume of cytoplasm, fairly constant for a particular cell type and usually increased in malignant neoplasms.
nucleolar-nuclear r. r. of volume of nucleolus to volume of nucleus, usually increased in malignant neoplasms.
nutritive r. the ratio or proportion of digestible protein to digestible non-nitrogenous nutrients in a ration for livestock.
P/O r. a measure of oxidative phosphorylation; the r. of phosphate radicals esterified (forming adenosine 5´-triphosphate from adenosine 5´-diphosphate) to atoms of oxygen consumed by mitochondria; normally, the r. is 3 (starting from NADH).P/O quotient;
respiratory exchange r. the r. of the net output of carbon dioxide to the simultaneous net uptake of oxygen at a given site, both expressed as moles or STPD volumes per unit time; in the steady state, respiratory exchange r. is equal to the respiratory quotient of metabolic processes.
segregation r. in genetics, the proportion of progeny of a particular genotype or phenotype from actual matings of specified genotypes. The test of a Mendelian hypothesis is the comparison of the segregation r. with the Mendelian r.
sex r. 1. the r. of male to female progeny at some specified stage of the life cycle, notably at conception (primary), at birth (secondary), or at any stage between birth and death (tertiary); 2. the r. of the numbers of males to females affected by a particular disease or trait.
signal-to-noise r. the relative intensity of a signal to the random variation in signal intensity, or noise; used to evaluate many imaging techniques and electronic systems.
standardized mortality r. the r. of the number of events observed in a population to the number that would be expected if the population had the same distribution as a standard or reference population.
systolic/diastolic r. a calculation from pulsed Doppler ultrasound determinations of blood flow velocities that reflects intrinsic resistance in an arterial blood vessel.
therapeutic r. the r. of the maximally tolerated dose of a drug to the minimal curative or effective dose; LD50 divided by ED50.
variance r. (F) the distribution of the r. of two independent estimates of the same variance from a gaussian distribution based on samples of sizes (n + 1) and (m + 1) respectively. Estimates are usually based on one such sample analyzed in such a way as to make them independent e.g., analysis of variance; and F may be used to test a null hypothesis that the observed differences among sample means is no greater than could readily be accounted for by chance.
ventilation/perfusion r. (Va/Q) the r. of alveolar ventilation to simultaneous alveolar capillary blood flow in any part of the lung; because both ventilation and perfusion are expressed per unit volume of tissue and per unit time, which cancel, the units become liters of gas per liter of blood.
zeta sedimentation r. (ZSR) the r. of the zetacrit to the hematocrit, normally 0.41 to 0.54 (41 to 54%); it is a sensitive indicator of the erythrocyte sedimentation rate (ESR) and, unlike the latter, is unaffected by anemia, which tends to elevate the ESR.
Browse Medical References: