such as digitoxin, deslanoside and lan- atoside croea react significantly with the antisera used in these kits. Inter- ference k m naturally ocaming ste- roids such ...
References 1. Huamann K. Quantitative h e p h e l o metrische Bestimmung von Rheumafac-
Tabb 1. Rwutts of Acid D i d a t i o n and immunoflxatlon of Mecroamylases A M add d-
toren mitteh IgG-beechichteter Latexparti-
kel. J Clin Chem Clin Bibchem 19, 11261130 (1Bal). 2. Singer JM,Plotz CM.The latex fixation teat. 1. Application to the m l o g i c diagnosis ofrheumatoid &tie.Am JMed21,892 (1956). 3. Finley PR,Hi& MJ, Williams RH,et al. Rata nephelometric measurement of rheumatoid factor in serum. Clin Chem 25, 1909-1914 (1979). 4. Painter PC,Lyon JM, E m JH,et al. P e d b n " of a new rata-nephelometric amay for rheumatoid factor,and ita correlation with tube-titer d t a for human aera and symvial fluid. Clin Chem 28,22142218 (1982). 5. Clot J, Sany J, Clot A. Doeage dea facbum rhumatoIdea par n6ph6lBm6trie h r . Rev Rhum 50,181-186 (1983).
France Deajarlais &jean Daigneault
LMpt. de Biochim. Hspital N o t r e - L h ~ 1660, Sherbmke East MonffBal, Qu?bec CaMda t12L 4K8 and LMpt. de Biochim. Uniuersitd de MonffBal
Macroamylase Not Always Evidenced by a Broad Band in Agmrose Gel Electrophoresis
To the Editor: Reporb on separation of amylase ieoenymes by electrophords on agar088 gel mention recognition of macroamylase by the OcCurrBnce of a characteristic blurring pattern or a broad band (1-3). Seven of eight cases of macroamylase recently diecovered in our clinic showed this broad band. The other displayed a Merent pattem a relatively sharp band at an unusual place in the ~ - g l O b u l i n-0% next to the normal bands for pancrab ic and salivary amylase. The pattern for this patient's urine lacked the extra band. Column chromatography with Sephadex G100 (4) confirmed that all eight sera contained high-molecularmam amylase complexes, which dieeociated at pH 3.4, albeit to various degrees (Table l). Aftar chromatographingthe dissociated macroamylase and concentrating the eluate in a Minicon CS 16, we determined by electrophol.eeis that the orighd complex in all c "contained, both pancreatic and salivary amylaee. M f " y l a 8 e m i a is well known to d t from the foxmation of a complex
-pk
kyl-
w,UR.
no. 1 2 3 4 5 6 7 8
1037 700 944 542
503 580 506
459
M" %
100 100 100 100 79 52 100 71
n Pb
KSb
67 37 50 34 unknown unknown
33 63 50 66
46
54
unknown
~o(C0mplQ
+ WA I ~ A - K+ IgA-A 1gA-K lg(3-K
w-K
+ 1gA-A
no IQdetedaMe Ig(3-K
W-A W K
'~intc#valfornonnal:mUiL. bP, l"tkand ealivafyisomymw of amyiaBe.
s:
between immunoglobulins and amylaee. Mostly IgA is involved, sometimes IgG.We applied immunohtion (6)to our eight "ylases,incubating the electrophoresis gels with anti-IgA, anti-IgM, anti-IgG, anti-rc, and anti-A antisera and,after washing, etaining these for amylase activity. The atypical 88111121sample appeared to contain a complex of amylase with I~G-K (Table 1, no. 6). We conclude that in some cases of macroamylasemia not all the 88111121 amylase is complexed. In those cases the amylase clearancekreatinine clearance ratio is within the normal range,0.008-0.038 (6).For example, in the atypical q l e (Table 1,no. 6) the ratio was O.ooS, in another (Table 1, no. 8) 0.018. In most cases of macroamylasemia the clearance ratio is decreased (6).Therefore recognition of macroamylases cannot always be based on a characteristicbluning pattern in agame electrophoreaie, or on a decreaeed amylase ClearandLTeatinine clearance ratio. References 1. Royee VL,Jensen DM. Development of an agamee gel elech.ophareeietechniquefor determining alpha-amylase ieoenzymea. clin chem 30,387490 (1984). 2. slcude 0.Ele&~&o&~'c eepf4ratioq de taction and variation of amylase h e n ~ ~ l m SCMd ea J Clin Lab Incad 35,4147 (1975). 3. Lderc P, Fomt JC. Electrophoretic determination of ieoamylaaee in aerum with commercially available reagente. Clin Chem 2 8 , 3 7 4 (1982). 4. Fridhandler L, Berk JE.Maeroamylaeemia A& Clin Chem 20.287-286 (1978). 5. Ritchie RF,Smith R I m m d t i o n I. General principles and application to agarOBB gel electrophoresis.Clin Chem 22,497499 (1976). 6. KlonofDC.Ma"yhmiaandother immunoglobulin-complexed enzgme dieordem. Weet J Med 133,392407 (1980).
C. Kammeraat J. A. de Jong
W. fir Clin. Chem. Diclconclreenhuis 4810 EV Bndor The Netherhnda
1078 CLINICAL CHEMISTRY, Vd. 31, NO. 6, 1985
Falsely inmasod R w u b for Digoxin in Sera from Patients with Liver Disease: Ten immunmuay Kit8 compared
To the Editor: Digoxin is a cardiac glyumide drug commonly p d b e d for the treatment of congestive heart Eailure and cardiac arrhythmias. Because of ita high toxicity and narrow therapeutic index, ita concentration in serum is routinely monitored. MO& laboratories use either commercially available digoxin radioimmunoassay (RIA) kita or nonisotopic immunoassay techniques such as enzymemultiplied immunoassay (EMIT)@ or flu0res"e polarization immunoassay. However, the preeence of a digoxin-like immunoreactive substance (DLIB) in the serum of neonah causes a falsely increaaed result for digoxin in sera assayed by commercial RIA kita (1-3). The serum of patients withrenalfailure has alaobeenreprb ed to contain DLB (4). Recently, we have shown the presence of DLB in the sera of patienta with liver disease (6).The purpoee of the present study was to extend our initial obaervations and to evaluate several commerQal ' immunoassay kita for interference by this "e. We collected sera from patienta with clinical and laboratory evidence of liver disease. W patienta had increased concentrations of total bilirubin and liver enzymes (aspartate and alanine aminohnderases)).Table 1shows the cause of liver dysfunction in the patients. We excluded from the study patients with renal impairment (serum creatinine concentration >176 pmol/L). The patienta' sera were stored frozen, and thawed just before analy-
eie. We used the following RIA kita to assay the samples for digoxin-like im'vity: Abbott Laboratariee, ~ m I , L 8 0 0 & cpieoxinq 4
3,
Im& kit); A " AF lington Heighta, IL 60006; ecton
Dickinoon Immunodiagnostice, Orangeburg, NY 10962-1294(solid-phase
Tabk 1. Clinical Diagnosis and Values tor DUS (nmoill) In Serum from 16 Patlent8 wlth Liver Disease Abbott
Metastatic liver disease
knrrBk TDx RIA rhvn &D R d 0.3 1.2 0.2 1.0 1.3
Uln.
-Comb
KAL MEN NYL
1.2
0.3
0.3
Alcoholkdrrhosis
c0.3 0.3 ~ 0 . 1 0.3 C0.3 0.4 c0.3 0.6 0.1 0.5 0.8 0.9 C0.3 C0.3 CO.1 C0.2 C0.3 CO.1
CO.1 0.2 C0.1
disease Metastatic lier disease
C0.3 C0.3 CO.1 C0.2 C0.3 CO.1
c0.3 0.7 0.1 0.5 0.9 c0.3 c0.3 cO.1 c0.2 c0.3
Abholiccirrhosis Metastatk lier
Alcoholic cirrhosis
Hepatoma, intrahepatic chemotherapy Infectious hepatitis Sepsis, spironolactone Acute fatty liver of Pregnancy Infectious hepatitis Metastatic lier disease Alcoholic hepatitis
Alcoholic cirrhosis, spironolactone Infectlous hepatitis Infectious hepatitis
1.0
1.4
C0.3
0.2 1.0 C0.3 C0.2
0.6
0.4
1.1 0.4
CO.1
c0.3 C0.2
0.3
0.1
0.2 cO.1
0.3 1.0 c0.3 C0.2
1.2 0.3
c0.3 c0.3 ~ 0 . 1~ 0 . 2 c0.3 ~ 0 . 3~ 0 . 1 0.3 0.3 c0.3 cO.1 c0.2 -
0.5 0.4 0.3
CO.1 0.1 CO.1
c0.3 0.3 0.6
c0.3 0.5 ~ 0 . 1 0.4 C0.3 - C0.1 C0.2
0.4
-
0.4 0.1
CO.1
c0.3 0.5 0.9 C0.3 0.2 C0.3
c0.3 0.6
-
0.5 0.4
-
-
0.1
0.2
- 0.2 -
c0.3 c0.3 0.2 c0.2 c0.3 0.5 cO.1 C0.3 C0.1
-
0.9
CO.l
0.4
CO.1
0.1
0.4
0.5
0.5
C0.3 C0.2 C0.3
C0.3 0.5 C0.3 0.6
0.8
0.6
- - -
