How to Convert from IDMS to Non-IDMS Serum Creatinine Values

Historically, serum creatinine was analyzed from a blood sample using a method called alkaline picrate.  In addition to creatinine molecules, though, it also “counted” non-creatinine molecules that falsely elevated the resulting value by as much as 20%.  This assay method was used for decades in the development of creatinine clearance estimates, such as the Cockcroft-Gault method.

Within the past 10-15 year, however, laboratories have largely moved to a new assay called IDMS (isotope dilution mass spectrometry).  This method does not detect the non-creatinine molecules, which means that the IDMS value is often 10-20% lower than the more conventional assay.  Because older equations, like Cockcroft-Gault, were created and validated using a non-IDMS assay, this poses a problem for estimating creatinine clearance (a surrogate for glomerular filtration rate) when using an IDMS-based lab assay.

Converting from IDMS to non-IDMS (Conventional)

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New Colistin (colistimethate sodium) Calculator

Pseudomonas aeruginosa nutrient agar

Colistin (in the form of colistimethate sodium, or CMS, in the United States) is an older, last-line agent for multidrug-resistant gram-negative infections.  Because of colistin’s complex pharmacokinetics and for historical reasons, there is a paucity of data regarding its dosing in patients with severe gram negative infections, particularly for those with concurrent renal dysfunction.

In one of the largest pharmacokinetic analyses of colistin to date, Garonzik et al. published a detailed analysis of CMS dosing in critically ill patients.  This analysis included dosing recommendations for patients with normal renal function, acutely changing renal function, intermittent hemodialysis (IHD), and continuous renal replacement therapy (CRRT).

ClinCalc is excited to announce our new colistin dosing calculator, which is based on the Garonzik pharmacokinetic recommendations.  This calculator was developed in coordination with Julie Ann Justo, PharmD, MS, BCPS, AAHIVP — an Assistant Professor at the South Carolina College of Pharmacy who specializes in infectious diseases and HIV pharmacotherapy. Continue reading

It’s Time to Say “Goodbye” to Vitamin D2 (ergocalciferol)

Prescription bottle of ergocalciferol (Vitamin D2) 50,000 IU

In the United States, vitamin D supplementation is primarily available as vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Although these two have historically been considered interchangeable and equipotent, the current body of literature strongly supports the preference of Vitamin D3 (cholecalciferol) over D2 (ergocalciferol).

Vitamin D2 versus Vitamin D3

Vitamin D3 (cholecalciferol) is produced by the human body in response to sunlight and is also available through dietary sources, such as fish. In contrast, vitamin D2 (ergocalciferol) is not produced in the human body, but is created by exposing certain plant-derived materials to ultraviolet light.

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Vancomycin Calculator Update – End of Infusion Peak (EoIP)

We’re releasing a major update to the calculation for our popular vancomycin calculator today. Briefly, the new update implements more advanced calculations when adjusting a vancomycin dose based on a trough level.

Drug Elimination during Vancomycin Infusion

When adjusting vancomycin based on a trough level, pharmacokinetic textbooks recommend estimating a vancomycin peak level using the following equation: Continue reading

ICU Trials Passes 100 Landmark Studies

Summarized landmark critical care trials on your mobile device is proud to announce that ICU Trials by ClinCalc, a mobile application that summarizes landmark critical care trials, has surpassed 100 studies in the app database!

With our most recent update on April 18th, the following recent and historic landmark trials were added:

  • MIDEX (2012): Dexmedetomidine vs. midazolam for mechanical ventilation
  • PAC-Man (2005): Efficacy of PA catheters in ICU patients
  • FEAST (2011): Fluid boluses in African children with severe infection
  • VSE (2013): Vasopressin, steroids, and epinephrine during cardiac arrest
  • MOPETT (2012): Alteplase for moderate PE
  • Brochard (1994): T-piece, SIMV, or PSV for ventilator weaning

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Speed Up Video Playback of The Top 250 Drugs Online Course

Increase Vimeo playback speed (Chrome extension)

At, we’re huge fans of listening and watching educational content at a faster than normal pace. Unfortunately, the video provider used for The Top 250 Drugs (online drug therapy course) does not allow for the ability to change playback speed.

If you’re using Google Chrome or Mozilla Firefox, though, you’re in luck!  Both web browsers have free extensions that allow you to speed up the playback speed of any video, including those on ClinCalc Academy.

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The Top 250 Drugs – Online Pharmacotherapy Video Course

ClinCalc DrugStats Database has been a bit quiet over the past year.  Our Twitter account has been mute, email updates rare, and website updates sparse.

Why the radio silence?

We’ve been diligently working on an exciting new product for the past year.  Quite literally, HUNDREDS of hours have been poured into the conception, creation, and implementation of this amazing new product.  Given this massive undertaking, we’ve kept website and mobile app updates to a minimum in order to expedite our production schedule. Continue reading

Really NEJM? Shocking Failure of the Peer Review Process for the ALBIOS Trial

Three nuts waiting to be cracked

The New England Journal of Medicine released three landmark trials this week.  Each trial directly addresses controversies in sepsis management that have been debated for a decade or longer: high versus low MAP goals (SEPSISPAM), a challenge to early goal-directed therapy (ProCESS), and albumin replacement (ALBIOS).

These trials will undoubtedly have a significant impact on future sepsis guidelines from SCCM, which is incredibly exciting.  Perhaps even more exciting is to see the dramatic improvement in early sepsis mortality between Rivers in 2001 (30.5 to 46.5%) and ProCESS (18.2 to 21%).

In pouring through each of these trials to provide a timely update to the ICU Trials mobile application, I was absolutely shocked by the failure of the peer review process in the ALBIOS trial.

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Visualizing the ACC/AHA ASCVD Pooled Cohort Equations

ASCVD Pooled Cohort Equations Visualization Tool - By Risk Factor

The newest ACC/AHA ASCVD Pooled Cohort Equations has been a very hot topic lately.  Our free web-based ASCVD tool and mobile applications have been very well received.  A number of ClinCalc readers have asked for a better understanding of the Pooled Cohort Equations — how is an ASCVD calculated?  How “strong” is each risk factor?

To help clinicians understand the new Pooled Cohort Equations, we’ve released a fantastic new visualization and graphing tool.  The tool is intended for the advanced clinician who wants to delve deeper into the equations and visualize the tool in a novel, interactive way.

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New Web-Based 10-Year ASCVD Risk Calculator (Pooled Cohort Equations)

ASCVD Calculator for Android and iOS



At ClinCalc, we’re very proud to announce the availability of both a web-based 10-year ASCVD Risk Calculator (also termed the Pooled Cohort Equations Calculator).  This risk assessment tool is recommended by the newly published 2013 ACC/AHA cholesterol guidelines to estimate 10-year risk of atherosclerotic cardiovascular disease (ASCVD).