The interference of drugs with clinical laboratory test results

Valyon, Martha1, Németh-Csóka, 1, and Naszlady, A2

Department of Clinical Chemistry1 and Outpatient Department of Cardiology2 of Koranyi State Institute of Tuberculosis and Pumonology


The interpretation of laboratory test results during drug administration is uncertain because of analytical and biological drug interferences with laboratory test results. Authors investigted the analytical and biological influences on clinical laboratory parameters during administration of Dopamine, theophylline, Cordaron, antituberculotics, cytostatics, respectively. The determination of the viability of white blood cell is recommended for the early detection of cell membrane damage during cytostatic treatment at an early stage.

Keywords: drugs, interferences, clinical chemical parameters


Routine clinical chemical test results of serum analites are influenced by adverse reactions of numerous endogenous and exogenous components. These our findings were reported earlier (Valyon et al. 1999), and a computer program was developed to indicate these effects in our laboratory reports (ibid). Several drugs have analytical or biological interferences with clinical laboratory test results (Kazmierczak and Catrou, 2000). Treatment of patients with one or two drugs, 7% and 16.6% of the test results were influenced, respectively (Kroll and Elin, 1994). In laboratory medicine, laboratory tests are usually indicated in such periods, when no interferences with the test results may be expected. There are some cases, however, where treatments can not be interrupted, so in these cases both the laboratory as well as the clinician has to take into account the possibility of the influence of drugs on laboratory test results. Some of our preliminary results in this field were published earlier (Németh-Csóka et al., 1999)

The aim of our present work was to detect the possibilities of drug interferences with laboratory test results in our special clinical environment. The special treatment groups in our institute were: Dopamine and Cordaron (Amiodaron) in the Department of Cardiology; theophylline in the Department of Bronchology; antituberculotics and cytostatics in the departments of respiratory diseases.

Materials and Methods

For the evaluation of the in vitro (analytical) and in vivo (biological) effects of drugs the two step method recommended by the IFCC (Kallner and Tryding, 1989) was used. The clinical chemical methods used in our experiments were described in our previous paper (Valyon et al., 1999). For the evaluation of drug interferences, the browsing program of DLI (Drug Laboratory Interference - Multimedica Turku, Finland) was used. The blood cell counts and white blood cell viability tests were carried out on a Cell-Dyn 4000 (ABBOTT) immune haematological analyser.

Results and discussion


Dopamine and Dobutamin (Dobutrex) are administered in infusion, sometimes for several days for patients in sever shock in order to prevent kidney failure. The molecular mechanisms of interference by Dopamine and Dobutamin have been recently described (Karon et al. 1998). They influence the methods which use hydrogen peroxide and horseradish peroxidase (the so called "Trinder reaction") for generating chromophores. These methods are: glucose, cholesterol, triglycerides, uric acid and enzymatic creatinine determinations. To define the effect and mechanism of the influence we examined the effect of Dopamine in vitro. First we made serial dilutions of Dopamine with pooled normal serum in concentration range between 0-200 mg/L and carried out the tests in triplicates using standard methods. The average values are summarised in Table I. That is the first step to prove the analytical interference of a drug, according to the IFCC rules (Kallner and Tryding, 1989).

The nagetive analytical Interference of Dopamine on "Tinder" type tests in increasing serum concentration


The serum concentration of Dopamine in mg/L





























Uric acid














The results are average values of 3-3 parallels. This experiment is the first step in order to demonstrate the analytical interference of Dopamine on cholesterol, glucose, uric acid and triglycerides tests recommended by IFCC gidelines (Kallner and Tryding, 1989).

The in vivo effects of Dopamine and Dobutamin are demonstrated with two cases:

In our first case the drug effect of serum analytical parameters were studied during Dopamine infusion, on the 3rd and 4th days of treatment. Our patient was a 60 y old woman (I.E.) in severe shock. The diagnosis at the admission was aplastic anaemia. The infusion was given at a rate of 5 mg/kg/min, for 60 hours.
















1,8 mmol/L






1,6 mmol/L






8,8 mmol/L



Uric acid



361 mmol/L


In our second case the changes of serum parameters during Dobutamin infusion of 5 mg/kg/min, 7 days were studied between the 3rd and 10th days. Our patient was a 58 y male (W.J.). The diagnosis was chronic nephritis. The indication of the Dobutamin treatment were threatening kidney failure and shock, respectively.
















42 mmol/L






290 mmol/L






3,9 mmol/L






5,3 mmol/L



Uric acid



777 mmol/L


The therapeutical levels of Dopamine and Dobutamin are less than 1 mg/L. However, during infusion therapy for several days, they might interfere with the test results of the Trinder type analytical methods, as serum uric acid, cholesterol and glucose determinations. As these infusions are used in cases of different diseases, one has to be aware of the fact that these might have negative influence even at therapeutic level on routine test results.

Cordaron (Amiodaron)

Cordaron is administered in ventricular arrhythmia cases per os or - in severe cases - intravenously. It is known that Cordaron can cause hepatic damage (Poucell et al. 1984), especially in patients sensitive to the drug. In the last year in our Department of Cardiology Cordaron was administered to more than 100 patients per os, and in some cases intravenously. One of these cases was demonstrated earlier (Pethes et al., 1998). Here we report our findings of one of our patients. A 60 y old woman, previously treated parenterally with Cordaron had to be treated intravenously 3 times with 300 mg Cordaron because of vital indication of severe ventricular arrhythmia. Within 3 days hepatitis-like symptoms developed. Therefore she was to be transferred to a hospital of infectious diseases. Nevertheless, as neither antigens of, nor antibodies to hepatitis B or C viruses could be detected in her serum, her hepatic symptoms were taken as signs of drug induced hepatic injury. The Cordaron adminsitration was stopped, and after several days the patient began to show a slow recovery from her hepatic damage. - Cordaron is known to bind to the vesicles of hepatocytes (which can be observed with electron microscope) and can cause - by inducing disruption of the vesicles - a hepatitis like disease (Poucell et al. -1998). From that time Cordaron therapy is more cautious and is controlled with higher awareness.


Theophylline is generally used in our departments of respiratory diseases. Here we had a patient with highly increased creatin kinase activity, without any cardiac involvement. It turned out that it was the consequence of an overdosage of theophylline. Theophylline overdosage can cause sever rhabdomyolysis (Ivano et al., 2000) with elevated CK level. Similar observations were reported earlier (Titley and Williams, 1992). On the basis of these findings we determined routinely CK acitvity in samples sent for theophylline therapeutic drug monitorong. In the last half year we have tested 240 samples. We could not demostrate any significant correlation between the two parameters. The average value of theophylline was 10.8 mg/L and that of CK activity 53.1 U/L respectively. Now we examine the CK activity only in samples with theophylline concentrations above 30 mg/L.

Antituberculotic drugs

In our Institute the usual treatment of patients with lung tuberculosis is the combination of the following drugs: Rifampicin (Tubocin, Rifazid), Rifabutin (Mycobutin), Isonicid (INH), Pyrazinamid (PZA), Ethambutol (Sural). In cases of infection with polyresistant mycobacteria, Amikacin and paraminosalicylic acid (PAS) infusions are used. It is known that INH + Rifampicin might cause sever liver damage (Girling, 1978; Lacroix et al., 1988; Thompson et al., 1995). Etambutol, Rifampicin increased the INH produced elevation of transaminase, phophatase and gamma-glutamintransferase activities. The side effects of the above drugs were evaluated by the scores recommended for the DLI browsing system. 72 tuberculotic patients were observed for drug interferences. 39 of these patient could be monitored for longer intervals and their testing could be evaluated. As approximately one half of this patient group suffered from chronic alcoholism, we have divided these patients into two groups, into clinically non-alcoholics and into clinically chronic alcoholics.

The effect of drugs on serum parameters (n = 39)

Most of the hepatic damage cases were found in patients treated with Rifabutin + INH. According to our earlier experiences with alcoholic patients, our interpretation of these test results is, that the serum parameters affected during the antituberculotics treatment are partly if not excusively really interferences with drugs used for therapy of these patients.



Serum parameters

Patients (n=39)




Lung tbc. 19

Lung tbc + alcoholism 20



GGT elevated





AST and ALT elevated





Total protein decreased





Albumin decreased





Uric acid elevated*




* PZA suppresses the tubular exretion of uric acid (Lacroix et al., 1988).

Cytostatic treatment

In our Institute about 2000 patients suffering from lung carcinoma are treated either surgically or with cytostatics and/or radiotherapy yearly (Ostoros, 1999). The administration of cytostatics may cause liver and kidney failure (Zhou et al., 1999), and bone marrow damage (Piscitelly et al., 1993, Ratain et al. 1990), respectively.

In our study 63 patients treated with cytostatics were monitored systematically. Liver and kidney function tests were performed and evaluated according to the score system suggested by DLI.





No of cases



Serum urea





Serum creatinine





Alkaline phosphatase










Aspartate aminotransferase





Alanin amino transferase





Creatine kinase MB





Serum total protein





Serum albumin




Changes in serum clinical chemical parameters of 63 patients on long-term continuous cytostatic treatment.

In nearly 50% of the patients some degree of liver or kidney damage could be demonstrated. This may be ascribed to the treatment. During the study one patient died because of bone marrow insufficiency. This was the main reason why we started also haematological monitoring of our patients on cytostatic treatment.

There are different approaches for individualising the dosage of anticancer therapy (Yihon and Evans, 1998). Among these are estimating the steady-state level of drugs, the AUC (area under the curve) of drugs (Ratain et al., 1990), by the DNA-adducts of Cisplatin (Reed et al., 1986) and their relation to the survival fraction of white blood cells.

For controlling the therapy we determined the blood cell count and the viability of white blood cells with a CellDyn 4000 Immun-haematologic Analyser (ABBOTT) before the treatment, after 7-8 days of treatment (nadir state) and before the new start of therapy 28 days later.

The changes of the percentage of viable white blood cells in different patient groups


Patient group

At start

After 24 hours






Controls (n=18)

97,0 ± 0,97

77,5 ± 7,9



Cytostatic treated (n=20)

96,3 ± 2,38

60,6 ± 18,3



After administration of Neupogen* (GCSF) (n=10)

96,5 ± 2,46

90,1 ± 2,83






Chest surgery (n=8)

95,5 ± 2,23

61,8 ± 10,9



Inflammatic lung diseases (n=8)

95,1 ± 2,1

55,7 ± 18,8



Other lung diseases (n=14)

96,9 ± 0,99

76,5 ± 10,0






Myelodysplasic patients (n=3)

91,3 ± 8,2

81,1 ± 15,3



Chronic lymphoid leukemia (n=3)

82,3 ± 14,2

39,0 ± 25,2


(See the paper of Brash et al., 1992)

71 patients suffering from solid lung carcinoma of non-small cell type were treated with Cisplatin, Etoposid, Rubomycin, Metothrexate, Vincristine. 23 patients out of these 73 patient group, and also other patients (altogether 54 patients) were evaluated. In the nadir state the white blood cell counts may decrease, or their viability might change. In normal cases the percentage of viable white blood cells is 97-98%. The viable cells exclude some dyes (Darzynkiewicz et al., 1992; Dive et al., 1992) from their cytoplasm by means of an active membrane process. The non-viable cells can be identified with flow cytometry by staining with fluorescent propodium iodide, with a dye which is normally excluded from cells with an intact membrane function. That is the measuring principle of the Cell-Dyn 4000 immun-haematological analyser. So we were able to determine the non-viable white blood cells by their fluorescence, during the CBC estimation. The detection of early cell membrane damage can be made more sensitive. This can be done with a second estimation of viable white blood cells after incubation of the samples for 24 hours, and so the detection of damaged cells is easier (Onofrio et al., 1995; Roth and Smitz, 1999). The effect of incubation on the viability of cell is demonstrated in Table II.

The changes of the viability of white blood cells after incubation at room temperature (average values of six normal blood samples)

Measuring within 3 hours after venip


After 24h incubation at room temperature uncture








First the viability of granulocytes, later that of lymphocytes decreases. Viability test: Cell-Dyn 4000 (ABBOTT).
(With May-Grünwald - Giemsa - stain no changes can be detected microscopically within 24 hours.)

In patient group A the 24 hrs viability of white blood cells of the cytostatic-treated patients is lower by 17% than that of the non-treated control group.

After Neupogen (Granulo-monocytic Colony Stimulating Factor) treatment the viability of white blood cell is completely recovered. In the interpretation of the change of the viability of white blood cells one has to be cautious. In severe surgical shock, in inflammatory diseases (pneumonias) the viability of white blood cells is decreased, see patient group B. In myelodisplasia and lymphoid leukemia the changes in cell viability are known (see also the results of Onofrio et al.) as it can also be demonstrated in our patients (see group C). Summarising the importance of the determination of the viability of white blood cells of patients treated with cytostatics, it seems to have two advantages:

  1. It is possible to predict individually the cell damage of the white blood cells in the nadir state. Therefore any sever bone marrow damage might be demonstrated in time and might be prevented.

  2. The efficacy of administration of the Neupogen in cases of sever granulocytopenia can be easily judged by controlling the viability of cells.

Concluding remarks

The data on drug effects in clinical chemistry have expanded enormously. The largest data base is the SWEDIS program. It contains 950 drugs, 370 tests, and 6500 references, respectively. The manual dealing with drug interferences, the "Drug Effect in Clinical Chemistry 1996" lists 81 drugs which can cause analytical interferences. Most of these drugs have biological effects which influence the interpretation of laboratory results. The data base is available on the Interne ( The data are updated continuously. We do hope that the adaptation of the SWEDIS data base can ensure further progress in our laboratory with the interpretation of our clinical chemical results during drug administration.

We would like to express our thanks to our clinician collegues Eva Salamon MD, J. Ostoros MD, and A. Wettstein MD for relevant clinical data.


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* Levélcím: Dr. Valyon Márta
Országos Korányi TBC és Pulmonolóliai Intézet
H-1529 Budapest, Pf. 1: