Clinical Chemistry 46, No. 6, 2000
dom have been using mainly PEG
precipitation techniques to identify
macroprolactinemia, but we urge
equipment manufacturers to address
this problem. As highlighted in these
two clinical cases, macroprolactin
needs to be identified early in a patient’s work-up to avoid unnecessary,
costly, and invasive procedures.
References
1. Leite V, Cosby H, Sobrinho LG, Fresnoza A,
Santos AM, Friesen HG. Characterization of big,
big prolactin in patients with hyperprolactinaemia. Clin Endocrinol 1992;37:365–72.
2. Fahie-Wilson MN, Soule SG. Macroprolactinaemia: contribution to hyperprolactinaemia in a
district general hospital and evaluation of a
screening test based on precipitation with polyethylene glycol. Ann Clin Biochem 1997;34:
252– 8.
3. Bjoro T, Morkrid L, Wergeland R, Turter A,
Kvistborg A, Sand T, Torjesen P. Frequency of
hyperprolactinaemia due to large molecular
weight prolactin (150 –170 kD PRL). Scand
J Clin Lab Investig 1995;55:139 – 47.
Fig. 1. Method mean prolactin concentrations
observed in a single donation of serum from
a patient with macroprolactinemia.
measured prolactin concentration
depends on the choice of reagent
antibody. Because the presence of
macroprolactin does not appear to
contribute to the hyperprolactinemic
syndrome in the majority of patients,
it is important to raise awareness of
the problem in clinical chemistry laboratories and with physicians. We
recommend that manufacturers of
prolactin reagents state in their product leaflets to what extent macroprolactin interferes in their prolactin assay and have available a validated
method to confirm the presence of
macroprolactin. It is also important
that manufacturers address the problem with prolactin assays to minimize reaction with macroprolactin.
In the meantime, polyethylene glycol
(PEG) precipitation has been shown
to be a valid screening test for macroprolactin when used with the Wallac DELFIA assay (2 ). It cannot, however, be used for all methods because
of interference from PEG, and it needs
to be validated with other assay systems before being brought into use.
Confirmation of the presence of
macroprolactin can be made by gel
filtration chromatography, but this is
time-consuming, costly, and beyond
the scope of most clinical laboratories. Laboratories in the United King-
Rhys John1*
Ian F.W. McDowell1
Maurice F. Scanlon1
Andy R. Ellis2
1
Departments of Medical Biochemistry
and Medicine
University Hospital of Wales
Heath Park
Cardiff CF14 4XW, United Kingdom
2
UKNEQAS for Peptide Hormones
Department of Clinical Biochemistry
Royal Infirmary
Edinburgh EH3 9YW,
United Kingdom
*Address correspondence to this author at: Department of Medical Biochemistry, University Hospital of Wales,
Heath Park, Cardiff CF14 4XW, United
Kingdom. Fax 44-2920-748383.
Plasma Ferritin in Acute
Hepatocellular Damage
To the Editor:
Plasma ferritin concentrations are increased in iron overload, liver diseases, infections, inflammatory conditions, and malignancy. Very high
concentrations (⬎10 000 ␮g/L) have
been described in Still disease (1 )
885
and less commonly in hemochromatosis. There are very few reports of
ferritin concentrations in patients
with acute hepatocellular damage
(AHD). A review of extreme increases in ferritin found that liver
disease was the cause of 20% of cases
but did not specify actual concentrations seen and did not differentiate
acute and chronic liver disease (2 ).
We have determined ferritin concentrations in AHD patients.
Plasma ferritins were measured in
eight patients who had plasma alanine aminotransferase (ALT) values
⬍100 U/L pre-AHD and ⬎1000 U/L
post-AHD. ALT, iron, and transferrin were measured on a Hitachi
917 (Roche Diagnostics), and ferritin
was measured on the ACS:180 (Bayer
Diagnostics).
The results for individual patients
are shown in Table 1. In one patient,
serum ferritin did not exceed the
upper limit of the reference interval
during AHD. This patient was irondeficient with a basal ferritin of 22
␮g/L.
The plasma ALT increased from a
basal mean (SD) of 45 (29) U/L to
2970 (1540) U/L during AHD, and
ferritin increased from 200 (130)
␮g/L to 18 260 (17 860) ␮g/L. The
mean plasma iron increased from 12
(11) ␮mol/L to 16 (19) ␮mol/L,
transferrin decreased from 27 (11)
␮mol/L to 22 (7) ␮mol/L, and transferrin saturation increased from 18%
(7%) to 31% (30%).
The rapid increase in ferritin in
AHD suggests that ferritin is present
in the cytosol of the hepatocytes.
There was significant (P ⬍0.01) correlation between the increase in ALT
and ferritin in AHD. Despite the
marked increase in ferritin in five of
six patients in whom iron and transferrin were measured, the transferrin
saturation increased above the reference interval in only one of these
patients.
In conclusion, ferritin concentrations were markedly increased after
AHD and are of no diagnostic value
during this time. These data imply
that ferritin and ALT are present in
the cytosol of the hepatocytes.
886
Letters
Table 1. Plasma ferritin in AHD.a
Age,
years
Sex
66
M
70
M
77
M
75
M
64
F
59
F
83
F
61
F
Pre-AHD
AHD
Pre-AHD
AHD
Pre-AHD
AHD
Pre-AHD
AHD
Pre-AHD
AHD
Pre-AHD
AHD
Pre-AHD
AHD
Pre-AHD
AHD
Date
ALT,
U/L
Ferritin,
␮g/L
Nov 12
Nov 13
Sep 28
Oct 3
Sep 11
Sep 12
May 19
Feb 21
Nov 11
Nov 12
Oct 4
Oct 5
Mar 19
Mar 22
Sep 28
Sep 30
27
1560
69
1720
54
4410
14
2530
28
5980
94
1790
15
3240
59
2510
22
211
206
7050
297
10 740
399
46 500
81
42 510
123
15 100
151
761
322
23 200
Iron,
␮mol/L
5
1
7
5
Trf,b
␮mol/L
Trf Sat,
%
27
24
22
19
9
2
16
12
Diagnosis
Post-operation, gastrectomy, hypotension
Septicemia
Cardiac arrest
4
12
26
49
25
26
2
2
17
15
35
31
44
29
17
14
12
40
37
79
28
45
6
7
Septicemia
Post-operation, liver transplant, ischemia
Post-operation, liver transplant, ischemia
Acetaminophen (paracetamol) overdose
Dissection of coronary artery because of
catheterization, hypotension
a
Reference intervals: ALT ⬍40 U/L; ferritin, 30 –500 ␮g/L for males, 20 –200 ␮g/L for females ⬍50 years, 30 –300 ␮g/L for females ⬎50 years; iron, 10 –30
␮mol/L for males, 9 –29 ␮mol/L for females; transferrin, 23– 43 ␮mol/L for males, 23– 46 ␮mol/L for females; transferrin saturation, 14 –53% for males, 13– 48%
for females.
b
Trf, transferrin; Trf Sat, transferrin saturation.
References
1. Schwarz-Eywill M, Heilig B, Bauer H, Breitbart A,
Pezzutto A. Evaluation of serum ferritin as a
marker for adult Still’s disease activity. Ann
Rheum Dis 1992;51:683–5.
2. Lee MH, Means RT. Extremely elevated serum
ferritin levels in a university hospital: associated diseases and clinical significance. Am J
Med 1995;98:566 –71.
Chotoo I. Bhagat*
Stephen Fletcher
John Joseph
John P. Beilby
Department of Clinical Biochemistry
PathCentre
Hospital Avenue
Nedlands 6009
Western Australia
Australia
*Author for correspondence. Fax 61-89346-3882; e-mail Chotoo.Bhagat@health.
wa.gov.au.
A High Factor II/Factor X Functional
Ratio Is Not a Useful Predictor of the
FII G20210A Gene Mutation in
Thromboembolic Patients Undergoing
Oral Anticoagulant Treatment
To the Editor:
A G3 A transition at nucleotide
20210 in the prothrombin gene has
recently been associated with venous
thromboembolism in a Dutch population (1 ). The prevalence of this genetic variation in Western countries
is 5–15% among thrombotic patients
and 1–5% in healthy controls (2–5 ).
The main pathogenic mechanism appears to be the increase of plasma
prothrombin (FII) because many carriers of the FII20210A mutation have
hyperprothrombinemia by functional assays. However, increased FII
is not specific for this mutation
(1, 3, 6 ). Even some carriers do not
exhibit hyperprothrombinemia because of the variability in vitamin K
metabolism or hepatic function. A
functional, rapid, low-cost assay,
preferably not influenced by the oral
anticoagulant (OA) (7 ) required by
many patients, would be desirable
for screening purposes. Because factor X (FX) has a half-life close to that
of FII, we used FX activity to control
for changes in concentrations of vitamin K-dependent factors. The ratio
of FII activity to FX activity (FII/FX)
was used to screen for subjects with
high FII activity during OA therapy.
We studied 123 outpatients objectively diagnosed with venous thromboembolism (59 men and 64 women;
mean age, 63 years; range, 17– 87
years) to identify a reliable screening
test for this genetic anomaly. All
were receiving OA (120 were receiving acenocumarol, and 3 were receiving warfarin). Informed consent was
required. The mean international
normalized ratio (INR) was 2.43
(0.76) with 66% of the patients in the
therapeutic range (INR, 2.0 –3.5) at
the time of sampling. The INR range
was 1.3–2.0 in 26% of the patients,
and none had an INR ⬎4.5. The subjects were classified as carriers and
non-carriers after a standard PCR assay for this prothrombin mutation (1 ).
For the standard functional clotting tests (FII:C/FX:C), we avoided
the large oscillations in the INR (especially during the first month of
anticoagulant therapy). We used deficient plasmas and recombinant
thromboplastin (Innovin®) from
Dade-Behring® on a Sysmex® CA6000® coagulometer. We calculated
the imprecision for plasmas with an
equivalent range of activity (⬍500
units/L). The intraassay CVs were
4.0% and 2.5%, and the interassay
CVs were 4.6% and 3.0% for the FII
and FX activities, respectively.
During OA therapy, FII:C remains
higher than FX:C (8 ). We observed
activities of 320 (120) vs 160 (90)
units/L, respectively (P ⬍0.0001).
The FII20210A allele was identified