Please check back frequently for important testing information

December 5, 2011

Testing Delay

We are currently unable to provide the following testing: Acetylcholine Receptor Antibody, Intrinsic Factor Antibody, Magnesium (RBC), Iron (24 hr Urine).  These tests are referred-out to another laboratory which is experiencing technical difficulties.  We expect testing to resume December 12, 2011.

Taking the time to provide advice to patients who require regular elective testing in anticipation of the holidays in December will facilitate management and possibly patient safety.  

It is inevitable that some patients will continue to require important testing (e.g., INR tests).   Communication of related critical or alert results has proven to be more difficult over the holiday period.

We recommend that patients who require testing by LifeLabs be advised to visit a LifeLabs Patient Service Center (PSC) no later than Monday, December 19^th.

• Saturday, December 24 - locations normally open on Saturday will close at noon
• Sunday, December 25 - Closed
• Monday, December 26 - Closed
• Tuesday, December 27 - Closed
• Saturday, December 31 - Closed
• Sunday, January 1 - Closed
• Monday, January 2 - Closed

Some regional PSCs will be open a half day on Saturday December 24^th (morning) to provide patient access over the extended holiday weekend. To verify the PSC hours of operation over the holiday period, please call the Central Call Center at 416-675-3637 or toll free 1-877-849-3637.

LifeLabs hopes you have a safe and happy holiday season.

June 29, 2011

Renin Analysis:  LifeLabs Changes to Method and Reporting

Plasma renin has an important role in the clinical assessment of hypertensive patients and is measured as plasma renin activity assay or as direct renin antigen.

Plasma Renin Activity (PRA)

Measurement of PRA in plasma involves quantitation of Angiotensin I by renin enzymatic activity acting on endogenous or exogenous plasma angiotensinogen. The concentration of Angiotensin I produced is proportional to the amount of active renin in the plasma. Currently, Lifelabs uses the Diasorin PRA radioimmunoassay and reports renin activity in ng/L/s. 

Note: the “ng” refers to the amount of Angiotensin I produced.

Direct Renin

Direct renin immunoassays measure the concentration of renin protein in the plasma. These methods are calibrated to the International Reference Preparation of human renin (68/356).

Direct sandwich immunoassays for renin protein offer improved precision and lower limits of detection, compared to PRA methods. These characteristics are particularly important as they provide a more accurate calculation of the Aldosterone/Renin Ratio at a low renin concentration, which is commonly seen in patients with primary aldosteronism.

In June 2011, LifeLabs will implement a direct renin chemiluminescent immunoassay (Diasorin Liaison) and, at that time, will begin to report renin in units of ng/L.

Note: In this case, the “ng” refers to the amount of renin protein.

A patient correlation between the Diasorin PRA RIA method and the Diasorin Liaison direct renin method was conducted.  Although a positive overall correlation was demonstrated between the two methods, many samples, particularly those with low results, deviated from the line of best fit.  It is important to remember that the two types of assays are measuring very different properties of renin. For these reasons, a universal factor for “converting” results from one method to the other is not available.

Aldosterone/Renin Ratio (ARR)

One of the primary clinical indications for renin measurement is the evaluation of patients with suspected primary aldosteronism (PA). The Endocrine Society, cosponsored by the European and International Societies of Endocrinology and Hypertension, recently published guidelines for diagnosis and management of patients with PA.² The guideline indicates that the ARR is the most reliable available means for screening for PA and is superior to measurement of potassium or aldosterone or of renin in isolation.

The guideline reports that the ARR is most sensitive when used in patients who have had unrestricted dietary salt intake before testing. It is recommended that samples be collected in the morning, after patients have been upright, (i.e. sitting, standing, or walking), for at least 2 hours.

Note: No interpretative guidelines are provided for samples collected from patients in a supine position.

While beyond the scope of this article, the reader may refer to the published guideline for a comprehensive list of factors, including medications, to be considered when preparing the patient and in interpretation of renin results.²

With the introduction of the new direct renin method, LifeLabs will also include calculation and report of the ARR for samples collected from patients in the upright position. ARR results will be calculated using Aldosterone measurements in units of “pmol/L” and Renin in units of “ng/L”. On the lab report, ARR results will be reported as “pmol/ng”.

Using these units and the methods specifically used by LifeLabs, the following guidelines have been developed to aid in the interpretation:

Author:  Peter Catomeris, PhD, FCACB, is a Clinical Biochemist for LifeLabs Ontario.

References

1.      Campbell DJ, Nussberger J, Stowasser M, Jan Danser AH, Morganti A, Frandsen E, and Menard J. Activity Assays and Immunoassays for Plasma Renin and Prorenin: Information Provided and Precautions Necessary for Accurate Measurement. Clin Chem (2009) 55(5): 867 – 877.

2.      Funder JW, Carey RM, Fardella C, Gomez-Sanchez CE, Mantero F, Stowasser M, Young WF Jr., and Montori VM. Case Detection, Diagnosis, and Treatment of Patients with Primary Aldosteronism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab (2008) 93(9): 3266 – 3281.

• a coloured baggie with a separate pocket for the Histopathology requisition. Please insert the Histology requisition into this pocket to protect against contamination from specimen leakage.
• The ‘small’ 5 ml container will change to a 20 ml container. The larger label provides more writing area to record the patient’s full name anda required second identifier (date of birth or health card number).
• The ‘medium’ 90 ml container will continue to be provided (containerdimensions unchanged).

• 20 ml #10114558
• 90 ml #10114559

• a copy of the OAHPP Labstract January 2010
• an example of the changes to the OAHPP Laboratory General Test Requisition list of tests performed by Public Health Laboratories