Usporedba metoda za određivanje osmolalnosti u serumu

master's thesis

• Title (english): Comparison of methods for the determination of serum osmolality
• Author: Renata Lipovec
• Mentor: Nada Vrkić (mentor)
• Committee member: Nada Vrkić
• Committee member: Roberta Petlevski
• Committee member: Sandra Šupraha Goreta
• Granter: University of Zagreb; Faculty of Pharmacy and Biochemistry; (Department of medical biochemistry and haematology); Zagreb
• Defense date and country: 2015-09-23, Croatia
• Scientific / art field, discipline and subdiscipline: BIOMEDICINE AND HEALTHCARE; Pharmacy; Medical Biochemistry

Abstract

Volumen tjelesnih tekućina i koncentracije elektrolita normalno se održavaju u vrlo uskim granicama usprkos velikim kolebanjima unosa hranom, metaboličke aktivnosti i okolišnih stresova. Razlike hidrostatskih tlakova s jedne i druge strane staničnih membrana su zanemarljive, pa hidratacija stanica ovisi o osmotskoj razlici između unutarstanične i izvanstanične tekućine. Osmolalnost plazme najvažniji je parametar za procjenu unutarnje ravnoteže vode u organizmu. Za mjerenje osmolalnosti koristi se osmometar, ali ne posjeduju ga svi laboratoriji pa se koriste različite metode izračunavanja.
Postoje različite metode za određivanje osmolalnosti plazme: izravno mjerenje osmolalnosti ili izračunavanje prema metodama:
Metoda A mOsmol/kg H2O = 2 x ([Na+]+ [K+]) + [glukoza] + [ureja]
Metoda B mOsmol/kg H2O = 1,86 x [Na+ ]+ [glukoza] + [ureja] + 9.
Cilj ovog istaživanja je odrediti osmolalnost na tri različita načina, međusobno usporediti dobivene vrijednosti, ustvrditi koliko se rezultati međusobno slažu i mogu li se metode međusobno uspoređivati i zamjenjivati. U istraživanju smo imali skupinu od 411 ispitanika koje je bila ujednačena po spolu. Uzorci su sakupljani na različitim odjelima KBC Sestre milosrdnice u jutarnjim satima. Osmolalnost seruma izmjerena je u uzorcima mjerenjem pomoću osmometra sniženjem ledišta otopine i izračunata je prema metodi A i metodi B iz izmjerenih varijabli u plazmi (koncentracije natrija, kalija, glukoze i ureje). Analizom podataka dobiveno je da se metode značajno razlikuju te da se međusobno ne mogu uspoređivati (P<0,0001). Pojedinačne varijable pokazale su slabiju, ali statistički značajnu povezanost s izmjerenom osmolalnošću osim ureje čija je koncentracija dobro povezana (rho=0,649; P<0,0001) i pravilnošću proporcionalno pridonosi osmotskom tlaku. Takav rezultat upućuje da su koncentracije sve 4 molekule kao 4 nezavisne varijable međusobno povezane pridonoseći osmolalnosti u nekom matematičkom zajedničkom odnosu. To je pokazao i model multiple regresije.

Abstract (english)

The volume of body fluids and electrolyte concentration is normally maintained in a very narrow range despite large fluctuations in food intake, metabolic activities and environmental stresses. Differences in hydrostatic pressures on both sides of the cell membrane are negligible, and hydration of cells depends on the osmotic difference between the intracellular and extracellular fluid. The plasma osmolality is the most important parameter for evaluating the inner water balance. The osmometer is used for measurement of plasma osmolality, but not all laboratories have one so they use different calculation methods. There are various methods for determining the plasma osmolality: direct measurement of osmolality or calculation by the following methods:
Method A mOsmol/kg H2O = 2 x ([Na+] + [K+]) + [glucose] + [urea]
Method B mOsmol/kg H2O = 1.86 x [Na+] + [glucose] + [urea] + 9
The purpose of this research was to determine the osmolality in three different ways, compare the obtained values with one another, say how the results are consistent and whether the methods can be compared and replaced with each other. The study included a group of 411 patients that was balanced by gender. Samples were collected at various departments of Hospital Center Sestre milosrdnice in the morning. The osmolality was measured by osmometer, in serum samples, lowering the freezing point of the solution and then calculated according to Method A and Method B with the variables measured in plasma (concentration of sodium, potassium, glucose and urea). Data analysis showed that the methods are significantly different and are not mutually comparable (P <0.0001). The individual variables showed weaker, but statistically significant correlation with the measured osmolality except urea whose concentration is well correlated (rho = 0.649; P <0.0001) and proportionally contributes to the osmotic pressure. This result indicates that the concentrations of all four molecules as four independent variables are interconnected contributing to the osmolality in a common mathematical relation. That is also demonstrated with the multiple regression model.

• Keywords: osmolalnost seruma; osmometrija; izračunavanje osmolalnosti
• Keywords (english): serum osmolality; osmometry; calculating the osmolality
• Language: croatian
• URN:NBN: urn:nbn:hr:163:847605
• Study programme: Title: Medical Biochemistry; Study programme type: university; Study level: integrated undergraduate and graduate; Academic / professional title: magistar/magistra medicinske biokemije (magistar/magistra medicinske biokemije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2016-02-17 15:18:02