| Abstract | Analiza mokraće jedan je od najčešće korištenih dijagnostičkih postupaka, a osim u dijagnostici koristi se kao uzorak
izbora za probir različitih bolesti te u praćenju tijeka bolesti i uspješnosti terapije.
Interferencije su glavni izvor predanalitičkih pogrešaka u laboratorijskoj medicini. Prisutnost različitih egzogenih ili
endogenih tvari može ometati mjerenje i dovesti do lažno povišenih ili lažno sniženih rezultata kemijske analize zbog čega
je potrebno za svaku pretragu poznavati moguće interferencije kako bi se izbjeglo izdavanje neispravnih nalaza i
usmjeravanje dijagnostike u krivom smjeru.
Askorbinska je kiselina snažan redukcijski i antioksidativni agens te najčešće korišteni vitaminski dodatak prehrani. To je
kemijski aktivna molekula koja se lako apsorbira iz probavnog trakta i brzo raspoređuje u tjelesna tkiva. Budući da vitamin
C pripada skupini vitamina topljivih u vodi, ako se unese u suvišku brzo se nepromijenjen eliminira iz organizma putem
mokraće. Posljedično, mokraća takvih pacijenata sadržava veću koncentraciju ovog vitamina od uobičajene. Zbog svoje
reduktivne sposobnosti askorbinska je kiselina poznati interferirajući spoj u biokemijskim testovima koji uključuju
indikatorske sustave s oksidazama i peroksidazama. Ovi se testovi koriste pri mjerenju glukoze, ukupnog kolesterola,
triglicerida i mokraćne kiseline, a askorbinska kiselina također može interferirati u određivanju bilirubina, fosfata, ureje,
kreatinina i različitih enzima.
S druge strane, šećerna je bolest najbrže rastuća kronična bolest u svijetu. Kod nekontrolirane šećerne bolesti, koncentracija
glukoze u krvi kontinuirano je visoka, što rezultira pojačanim izlučivanjem glukoze putem bubrega. Glukoza je
monosaharid za koji je poznato da može imati utjecaj na različite metode kemijske analize. Najpoznatija je interferencija
glukoze u određivanju kreatinina Jaffeovom metodom, ali interferencija je do sad uočena i prilikom određivanja albumina
i pojedinih elektrolita.
Cilj ovog istraživanja bio je utvrditi utječu li povišene koncentracije askorbinske kiseline i glukoze na laboratorijske
pretrage u mokraći. Istraživanje je provedeno u Kliničkom zavodu za kemiju, KBC Sestre milosrdnice. Za istraživanje je
korišten nasumično odabrani uzorak 24 satne mokraće, a parametri koje smo određivali su ukupni proteini, albumin,
amilaza, natrij, kalij, kloridi, kalcij, anorganski fosfati, magnezij, kreatinin, ureja i mokraćna kiselina. Pripremljeno je 7
uzoraka različite koncentracije dodanog interferenta. Askorbinska je kiselina pripremljena u koncentracijama 0, 0,2, 0,4,
0,5, 1, 2 i 5 g/L, a glukoza u koncentracijama 0, 10, 20, 30, 40, 50 i 60 mmol/L. Sva mjerenja rađena su u duplikatu, za
statističku analizu korišten je program Microsoft Excel.
Rezultati istraživanja nisu pokazali statistički značajno odstupanje prema definiranim kriterijima prihvatljivosti za
određivanje koncentracije albumina, amilaze, natrija, kalija i fosfata. Međutim, askorbinska je kiselina interferirala u
određivanju kloridnih, kalcijevih i magnezijevih iona. S druge strane, povišena koncentracija glukoze interferirala je s
određivanjem proteina, kalcija, magnezija, kreatinina, ureje i mokraćne kiseline.
Na temelju dobivenih rezultata zaključujemo da rezultate analize određenih parametara kod pacijenata koji imaju povišene
koncentracije glukoze i/ili askorbinske kiseline u mokraći treba tumačiti s oprezom. |
| Abstract (english) | Urine analysis is one of the most used diagnostic procedures, and in addition to being diagnostic tool, it is used as the
sample of choice for screening various diseases, in monitoring the course of the disease and treatment progress.
Interferences are a major source of preanalytical errors in laboratory medicine. The presence of various exogenous or
endogenous substances can interfere with the measurement and lead to falsely elevated or falsely reduced results of
chemical analysis, which is why it is necessary to know possible interferences for each test to avoid issuing incorrect
laboratory reports and directing diagnostics in the wrong direction.
Ascorbic acid is a powerful reducing and antioxidant agent and the most commonly used vitamin food supplement. It is a
chemically active molecule that is easily absorbed from the digestive tract and rapidly distributed to body tissues. Since
vitamin C belongs to the group of water-soluble vitamins, if taken in excess, it is quickly eliminated unchanged from the
body through the urine. Consequently, the urine of such patients contains a higher concentration of this vitamin than usual.
Due to its reductive ability, ascorbic acid is a known interfering compound in biochemical tests that include indicator
systems with oxidases and peroxidases. These tests are used to measure glucose, total cholesterol, triglycerides and urate,
while ascorbic acid can also interfere with the determination of bilirubin, phosphate, urea, creatinine and various enzymes.
On the other hand, diabetes is the fastest growing chronic disease in the world. In poorly controlled diabetes, the
concentration of glucose in the blood is continuously high, which results in increased excretion of glucose through the
kidneys. Glucose is a monosaccharide that is known to affect various methods of chemical analysis. The most well-known
is the interference of glucose in the determination of creatinine by the Jaffe method, but the interference has so far also
been observed in the determination of albumin and certain electrolytes.
The aim of this research was to determine whether elevated concentrations of ascorbic acid and glucose affect laboratory
tests in urine. The research was conducted at the Clinical Institute of Chemistry, KBC Sestre milosrdnice. A randomly
selected 24-hour urine sample was used for the research, and the parameters we determined were total proteins, albumin,
amylase, sodium, potassium, chlorides, calcium, inorganic phosphates, magnesium, creatinine, urea and uric acid. 7
samples of different concentrations of the added interferent were prepared. Ascorbic acid was prepared in concentrations
of 0, 0.2, 0.4, 0.5, 1, 2 and 5 g/L, and glucose in concentrations of 0, 10, 20, 30, 40, 50 and 60 mmol/L. All measurements
were made in duplicate, while the Microsoft Excel program was used for statistical analysis.
The results of the research showed no statistically significant deviation according to the defined acceptance criteria for
determining the concentration of albumin, amylase, sodium, potassium and phosphate. However, ascorbic acid interfered
in the determination of chloride, calcium and magnesium ions. On the other hand, elevated glucose concentration interfered
with the determination of protein, calcium, magnesium, creatinine, urea and uric acid.
Based on the obtained results, we conclude that the results of the analysis of certain parameters in patients with elevated
concentrations of glucose and/or ascorbic acid in the urine should be interpreted with caution. |
