Immunofluorescence on proteinase XXIV-digested paraffin sections


theless, in our fully adjusted model, the 95% CI for the
hazard ratio associated with the administration of
paricalcitol versus calcitriol included the point estimate
reported by Teng et al.3 Paricalcitol appears to confer
no survival advantage over doxercalciferol. The point
estimates for hazard ratios for doxercalciferol versus
paricalcitol ranged from 0.99 to 1.06 and each 95% CI
included 1.0. However, we cannot exclude the possibility
that doxercalciferol may be associated with a small benefit
or disadvantage over paracalciferol.

Our retrospective study reflects clinical practice. Since
different vitamin D preparations became available at
different times, the treatments were not simultaneous, and
switching was the major cause of censoring. The vitamin D
analogs were not dosed according to KDOQI guidelines,
since most of the study occurred before these were published.

1. Sprague SM. Mortality risk among hemodialysis patients receiving
different vitamin D analogs. Kidney Int 2006; in press.

2. Tentori F, Hunt WC, Stidley CA et al. Mortality risk among hemodialysis
patients receiving different vitamin D analogs. Kidney Int 2006; 70:
1858–1865.

3. Teng M, Wolf M, Ofsthun MN et al. Activated injectable vitamin D and
hemodialysis survival: a historical cohort study. J Am Soc Nephrol 2005;
16: 1115–1125.

F Tentori1, WC Hunt1, CA Stidley1, MR Rohrscheib1, EJ Bedrick1,

KB Meyer1, HK Johnson1 and PG Zager1
1Dialysis Clinic Inc. (DCI), Quality Management, Albuquerque, New Mexico,

USA

Correspondence: F Tentori, Dialysis Clinic Inc., Quality Management, 1500

Indian School Rd NE, Suite 200, Albuquerque, New Mexico 87102, USA.

E-mail: francesca.tentori@dciinc.org

Immunofluorescence on
proteinase XXIV-digested paraffin
sections
Kidney International (2007) 72, 896; doi:10.1038/sj.ki.5002495

To the Editor: In their comparison of immunofluorescence
(IF) on frozen sections with pronase-digested paraffin
sections, Nasr et al.1 found that pronase digestion was a
useful technique for IF on paraffin (IF-P) sections. However,
the sensitivity of this technique was low for membranous
glomerulopathy and anti-glomerular basement membrane
disease (50 and 20%, respectively), which was mainly due
to weak staining of IgG (immunoglobulin G).

In our laboratory, we use bacterial proteinase XXIV
(Sigma, St Louis, MO, USA), as described by Bancroft and
Gamble,

2 instead of pronase. We compared IF-P on
proteinase XXIV- and pronase-digested paraffin sections.
We selected five cases of lupus nephritis that showed full-
house fluorescence staining on frozen sections. In all cases,
staining intensity was similar or better on proteinase XXIV-
digested slides, and less background was observed. Impor-
tantly, staining for IgG and C1q was more intense in sections
digested with proteinase XXIV than in those digested with

pronase. In addition, we tested five cases of anti-glomerular
basement membrane disease. One of these was negative after
pronase, as well as after proteinase XXIV digestion, one was
positive with both techniques, whereas the remaining three
were positive only after proteinase XXIV digestion. Finally, in
nine cases of membranous glomerulopathy, diagnostic IF-P
staining for IgG was obtained in six cases after pronase
digestion and in five cases after proteinase XXIV digestion.

In conclusion, we agree with Nasr et al. that IF-P is a
valuable salvage technique for renal biopsies. To this, we
would like to add that IF-P on sections digested with
proteinase XXIV is generally more sensitive than IF-P on
pronase-digested sections.

1. Nasr SH, Galgano SJ, Markowitz GS et al. Immunofluorescence on
pronase-digested paraffin sections: a valuable salvage technique for renal
biopsies. Kidney Int 2006; 70: 2148–2151.

2. Bancroft JD, Gamble M. Theory and Practice of Histological Techniques,
5th edn. Churchill Livingstone, London, 2002, pp 450–451.

K van der Ven1, TQ Nguyen1 and R Goldschmeding1
1Department of Pathology, University Medical Center Utrecht, Utrecht,

The Netherlands

Correspondence: R Goldschmeding, Department of Pathology, University

Medical Center Utrecht, Utrecht, The Netherlands.

E-mail: R.Goldschmeding@umcutrecht.nl

Machiavelli and urinalysis
Kidney International (2007) 72, 896–897; doi:10.1038/sj.ki.5002496

To the Editor: I read with great interest the article on the
history of urinalysis in Western culture by Armstrong.1 It
gives a detailed outline of how uroscopy developed into a
prominent medical diagnostic tool, and later was abandoned
due to the poor scientific basis of such practice. In Dr
Amrstrong’s article, however, it is not mentioned that
uroscopy was so popular to be included in the most famous
play by Niccolò Machiavelli, ‘La Mandragola (The Man-
drake)’,

2,3 making fun of presumptuous physicians and
credulous patients. In another important paper on uroscopy
by Voswinckel,4 the contribution of Machiavelli is not
mentioned as well.

Niccolò di Bernardo dei Machiavelli (May 3, 1469 to June
21, 1527) was an Italian political philosopher. He is a central
figure of the political component of the Italian Renaissance,
most widely known for his treatises on realist political theory
(The Prince). However, he also was a musician, poet, and
romantic comedic playwright.

The Mandragola has been widely performed and very
popular since the sixteenth century. The title comes from
the popular tale that a woman who drinks a potion made
from the mandrake root is certain to conceive a child, the
only drawback being that the man with whom she first has
sex after taking the potion will die within 8 days. The story
evolves around Callimaco, a lovesick Florentine who
came form Paris to conquer the heart (and the graces) of
Lucrezia, the beautiful young wife of Messer Nicia Calfucci, a

896 Kidney International (2007) 72, 895–898

l e t t e r t o t h e e d i t o r