Drug Interferences in
P R E V E C A L D E P A R T M E N T
T his is the first in a series of Bulletins on the account a patient’s clinical history as well as their current
interferences caused by drugs in clinical trails that the
state of health, since underlying illnesses may affect
Prevecal Department at BioSystems is going to issue for
laboratory professionals. Given the large number of active
compounds interfering with results, each bulletin will deal
Interferences are also an important cause of the poor
with a single test so that the information given can be as
interpretation of a patient’s analytical results. There are
The diagnosis of a patient should not only be based on
the findings of one trial but also include clinical and
laboratory data. There are many variables conditioning
analytical results and these must always be borne in mind
In this bulletin we are going to focus on drug interferences
in order to give a correct diagnosis. These variables can
although mention will also be made of those concerning
be divided into three main categories.
methodology. The total number of drugs or active
compounds producing effects on laboratory tests is too
large for them to be rigorously set out in this bulletin.
The intention of the Prevecal Department at BioSystems
is to boil down all the most active compounds to those
that have a greater relationship with a specific test. There
Preanalitical variables are a long list of conditions that
is an excellent reference book on the subject, Young DS.
take into account a patient’s characteristics and lifestyle.
Effects of drugs on clinical laboratory tests, 5th ed. AACC
Some of these factors are age, gender, race, diet, alcohol,
which contains the greatest number of drug
tobacco and coffee consumption, obesity, physical
interferences. This book is a must for any clinical
exercise, etc. It is also of basic importance to take into
(Glycerol Phosphate Oxidase/Peroxidase
Triglycerides are glycerol and fatty acid esters that comefrom a dietary source or are synthesised mainly in the
ACETYLCHOLINESTERASE (AChE) INHIBITORS
liver. They are transported in plasma in the lipoproteinsand are used by adipose tissue, muscles and others. Their
4.2 mg/dL average decrease occurs with regard to
main function is to provide energy to cells. High serum
reference values in treatments lasting 12 months,especially in patients with hypercholesterolemia
concentrations of triglycerides may be due to hepatobiliarydisorders, diabetes mellitus, nephrosis, hypothyroidism,
alcoholism, familial hyperlipoproteinemia type IV and Vand others.
Moderate to average hypertense patients treated with100 mg/day for 24 weeks caused 10.6% average
reduction. Patients with essential hypertension treatedwith 75 mg/day showed average reduction from
Each point is the average of three. Horizontal lines show
181.8±26.4 mg/dL to 154.6±18.8 mg/dL.
the tolerance for the value obtained in the presence ofinterferent, calculated as: the average in the absence of
interferent ± 3 x interseries standard deviation.
Patients with grade 1 diastolic hypertension treated with
Sample: human serum without (a) and with growing
5 mg/day caused average change from 1.6±1.16 mmol/Lto -0.36±0.06 mmol/L after 12 months treatment and to
–0.14±0.08 mmol/L after 48 months. Significant reductionof average from 1.74±1.04 mmol/L to 1.63±0.054 mmol/Lreported for patients with essential hypertension treated
Serum triglyceride concentration increase reported. Non
uniform increase with variations depending on
hypertension type and patient’s history.
Plasma triglyceride concentration increase reported.
Increase more acute in average, moderate and essential
hypertense patients than in patients with
hypercholesterolemia and normocholesterolemia.
Triglyceride concentration increase in hypertense patients
treated with beta blockers as opposed to those not treated
As can be seen in the graphs, hemoglobin (10 g/L) does
Serum triglyceride concentration baseline decrease
not interfere while bilirubin (2.5 mg/dL) does.
Clear reduction of serum triglycerides reported. Range
Estrogens reported to increase triglyceride concentration
oscillates between 27% and 58% depending on pathology
in postmenopausal women from 15% to 20% above the
Triglyceride concentration reduction between 3% and 9%
Significant triglyceride concentration reduction in patients
reported depending on pathology type and length of
with chronic dialysis reported after 4 months treatment.
16% triglyceride concentration increase with a low dosage
Triglyceride concentration reduction between 30% and
60% reported depending on pathology type and lengthof treatment.
NON INTERFERING DRUGS
Triglyceride concentration reduction between 12% and
The following drugs do not interfere at therapeutic
25% reported depending on pathology type and length
Acetylsalicylic acid, Amphotericin B, Ampicillin, Ascorbicacid, Barbital, Bromazepam, Chloroquine, Codeine,
Diazepam, Gentamicin, Ibuprophen, Morphine, PenicillinG, Phenobarbital and Sulphanilamide.
Triglyceride concentration baseline decrease from5.02±1.22 mmol/L to 2.16±0.46 mmol/L after 3 monthsand to 2.0±0.30 mmol/L after 6 months treatmentreported.
Significant reduction of triglyceride serum concentrationbetween 15% and 26% reported.
Patients treated for hypothyroidism show acute reduction
of serum triglyceride concentration. Baseline reductionmay be higher than 30%.
Over 40% above baseline serum triglyceride concentration
increase when oral contraceptives administered.
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Eili Klein,* David L. Smith,† and Ramanan Laxminarayan* Hospital-acquired infections with Staphylococcus au- increased, fi rst to other hospitals and then into the commu- reus , especially methicillin-resistant S. aureus (MRSA) in-nity ( 5 ). By the late 1960s, >80% of community- and hos-fections, are a major cause of illness and death and impose pital-acquired S . aureus isolat
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