amastyleinsider

May 31, 2012

AMA Style Insider Responds

Filed under: meta-blog,quizzes — amastyleinsider @ 1:03 pm
Tags: , ,

We love comments. (From real people, that is. Spambots, you can stop any time.)

We love comments like, “Great blog!” We even love comments like, “You are wrong about every single thing related to medical editing, your mother was a hamster and your father smelled of elderberries, goodbye.” Both of those require simple responses—I like “Thanks!” for both, to be honest. For the latter, I would be charitable and not even comment on the comma usage.

Every once in a while someone will leave a critical comment that requires a longer response, and sometimes the consultation of outside experts. That was the case with this Quiz Bowl post on units of measure. A reader wrote:

A big problem with the AMA manual is a lack of consideration significant figures. The conversion factor listed in the online “SI Conversion Tables” section from feet to centimeters is 30. That’s wrong. Let’s say I try to convert my height (6.0000 feet) into centimeters. The “.0000″ means that my measurement has 5 significant figures. Significant figures are important in science and health care.

I start with the only unit conversion between customary and metric that matters: 2.54 centimeters equals exactly 1 inch. This is the only conversion that matters because it is a definition. There are infinite significant figures.

Here is what happens if I use the “SI Conversion Tables” section of the AMA manual of style:

6.0000 feet * 30 = 180 centimeters

Here is what happens if I use math and pay attention to significant figures:

6.0000 feet * (12 inches/1 foot) * (2.54 cm)/(1 inch) = 182.88

Where did those extra 2.88 centimeters come from? They came from a a conversion factor that was wrong.

For the same reason as above, your answer to the first problem is wrong.

7.2 inches^2 * (((2.54 cm)^2)/((1 in)^2)) = 46.45 (assuming 4 significant figures, to demonstrate the inaccuracy of your conversion factor)

This isn’t just an academic exercise. A text for editors shouldn’t have errors like this.

We made “hmmm” noises for a while but finally drafted a response to post here, since a shameful amount of time has gone by since the original comment.

You raise an important point about the significance of significant digits. The Manual addresses this in section 20.8.1 and, in chapter 18, where the conversion table is embedded that shows conversions for inches to centimeters, there is a caution that results should not be reported beyond the appropriate level of precision.  It is critical to ascertain the precision needed for the clinical context of the conversion. If you only need significance to 1 place beyond the decimal (7.2 inches) to accurately describe tumor size, then the 2 significant digits of the result should be fine and the clinical difference between 46.8 and 46.5 is probably not important.

It’s entirely possible that the final 3 words of that paragraph are the equivalent of a thrown gauntlet to someone out there—if so, we’re willing to continue the conversation in the comments to this post.—Brenda Gregoline, ELS

February 28, 2012

Quiz Bowl: SI vs Conventional Units

Filed under: quizzes — amastyleinsider @ 1:51 pm
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Welcome back, quiz bowl participants. Our very first quiz bowl, which appeared on this site on May 5, 2011, dealt with format, style, and punctuation of units of measure. Now we’re back to delve even further into the intriguing and ever-changing world of units of measure style. The following is a sample of one of the questions that appears in this month’s AMA Manual of Style quiz on SI vs conventional units (http://www.amamanualofstyle.com/). Answer the question based on your understanding of section 18.5 of the AMA Manual of Style.

The mean 2-dimensional area of the largest metastasis was 7.2 sq in.

So, what do you think? This one isn’t really too hard. Here’s the answer (use your mouse to highlight the text box):

The mean 2-dimensional area of the largest metastasis was 46.8 cm2.

Measurements of length, area, volume, and mass are reported in metric units rather than English units. To convert square inches to square centimeters, multiply by 6.5 (§18.5.1, Length, Area, Volume, Mass, pp 794-795 in print).

Let’s try a more challenging question.

Admission laboratory tests revealed the following: serum creatinine, 0.9 mg/dL; serum urea nitrogen, 11 mg/dL; serum albumin, 39 g/L; and prothrombin time, 11.5 seconds.

Yes, this one is definitely harder. Here’s the answer:

Admission laboratory tests revealed the following: serum creatinine, 0.9 mg/dL (to convert to micromoles per liter, multiply by 88.4); serum urea nitrogen, 11 mg/dL (to convert to millimoles per liter, multiply by 0.357); serum albumin, 3.9 g/dL (to convert to grams per liter, multiply by 10); and prothrombin time, 11.5 seconds.

For laboratory values, factors for converting conventional units to SI units should be provided in the article. In text, the conversion factor should be given once, at first mention of the laboratory value, in parentheses following the conventional unit (§18.5.10, Laboratory Values, pp 797-816 in print). Although the AMA Manual of Style recommends writing out units of measure when no numbers are reported (eg, micromoles per liter), some journals may prefer to use abbreviations when listing SI conversion factors (eg, mmol/L).

Need some more practice? Subscribe to the AMA Manual of Style online and take the full quiz. If you’re new to the site, check out some of our other quizzes as well.—Laura King, MA, ELS

August 2, 2011

Questions From Users of the Manual

Filed under: frequently asked questions — amastyleinsider @ 11:15 am
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Q:   If one has a list of laboratory values, does one have to keep repeating the units of measure, eg, albumin levels of 3.8 g/dL, 3.9 g/dL, and 4.0 g/dL, or is once enough, eg, albumin levels of 3.8, 3.9, and 4.0 g/dL.

A:  No, the unit of measure does not have to be repeated:  albumin levels of 3.8, 3.9, and 4.0 g/dL is fine.  The exception to this is for units of measure that are set closed up to the number or value that they follow, such as the degree sign or the percent sign.  In these cases, the unit of measure should be repeated:  38%, 45%, and 53%.

Q:   What abbreviation does JAMA/Archives prefer for adjusted odds ratio?

A:   We prefer AOR.

Q:   Is “data on file” acceptable in a bibliography or in parentheses in the text?  I don’t see this in the Manual.

A:   The phrase “data on file” is a little vague.  What a reader who’s interested in more information might really want to know is how the author of the manuscript saw the data (and how, perhaps, the interested reader might be able to see it too).  Something more granular about how the author came upon the information would be more helpful.  For example, did the author learn about the information through a personal communication (and is that personal communication the “data on file”?)?  If so, see 3.13.9 in the Manual for how to style this as an in-text references.  Is the “data on file” an internal memo at an institution and, if so, does it have a document number that could be listed in the reference list?

Q:   Would you hyphenate “quality of life” when it’s used as a noun as well as when it’s used as an adjective?

A:   We usually hyphenate as an adjective and not as a noun.—Cheryl Iverson, MA

May 5, 2011

Quiz Bowl: Units of Measure

Filed under: editing process,punctuation,quizzes,usage — amastyleinsider @ 11:10 am
Tags: , , , ,

Welcome, participants, to the AMA Manual of Style Quiz Bowl. Every month at http://www.amamanualofstyle.com/, we offer subscribers a quiz on different aspects of the manual that help participants master AMA style and improve their editing skills. Previous quizzes have covered topics as varied as correct and preferred usage, genetics, tables, figures, and ethics, as well as numerous other subjects. In this blog, we will offer a sample question from each month’s quiz to whet your appetite. This month’s quiz is on Units of Measure: Format, Style, and Punctuation. So, here goes.

Edit the following sentence based on your understanding of section 18.3 of the AMA Manual of Style.

A total of 50 mg of etanercept were administered subcutaneously twice weekly for 12 weeks.

Well, how did you do? Did you identify the problem? Here’s the answer (use your mouse to highlight the text box):

A total of 50 mg of etanercept was administered subcutaneously twice weekly for 12 weeks.

Units of measure are treated as collective singular (not plural) nouns and require a singular verb (§18.3.3, Subject-Verb Agreement, p 791 in print).

So, did you enjoy this tidbit? If you are not sated, subscribe to the AMA Manual of Style online and take the full quiz.—Laura King, MA, ELS

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