CORRESPONDENCE

Currently, the cost for materials to synthesizeGHB IS approximately $50/1 00 g, and the costfor GBL is $156/L.

Since our reports, we have received manyrequests from physicians on proper methodsfor GHB toxicologic testing GHB is readilydetected uSing standard gas chromatography­mass spectrometry(GC-MS) methods. GHBcan be routinely detected and levels quanti­fied In samples of serum, plasma, blood, andurine provided specific request is made tothe toxicology laboratory so that search forthemass spectrometry pattern is performed. IfGC-MS testing is unavailable locally, specI­mens can be frozen and tested elsewhere at alater date Testing is available from severalnational forensic and toxicology laboratories,and costs approximately $100 per specimen(National Medical Services, Willow Grove,PA, 800-522-6671). For cases of sexual assault,Hoffman-La Roche provides acombined GC­MS assay free of charge for flunitrazepam(Rohypnoll. GHB, and alcohol (Hoffman-LaRoche Sexual Assault Hotline; 800-608-6540).

Since our report. an additional GHB­related death has been reported, bnnging thetota Iknown deaths to 10.2Because of thewidespread use and availability of GBL Inindustry, It is unlikelythatthis substancewill soon be regulated. Ease of GHB synthe­sis, as well as substitution of GBL for GHBabuse, may lead to epidemics of abuse. Toreaders who may participate in illiCit use ofthese substances, we reiterate the inherentdanger of noncontrolled use, due to directeffects of GHB and GBL. to further toxicitywhen these are combined With alcohol orother drugs of abuse, and to toxic effects ofby-products and impunties associated Withhome synthesis. To phYSicians, we reiteratethe need for suspicion of GHB (or related)tOXICity in cases of unknown ingestIOn withaltered mentation. Suspected cases shouldbe treated With Vigilance toward respi ratoryfailure, as detailed previously, with appro­pnate toxicologiC testing and law enforce­ment notification.

JamesLI, MDDIVision of Emergency MedlcmeMount Auburn HospitalHarvard Medical SchoolCambndge, MA47/8/97564

1 Fowkes S GHB Report to the Californw LegrslatureMenlo Park. CA Cogmtlve Enhancement ResearchInstItute. 1998

2 KGTV News. San DIego Woman launches Intenlct em­sade agaInst popular Illegal party drug [broadealtJ June29,1998

In reply:

We agree with the need to be aware of GBLand that mass spectrometry cannot differen­tiate GBL ingestion from GHB ingestion In

unne or serum samples. However, It is possi­ble to differentiate GHB and GBL in urinesamples, by using gas chromatography andflame IOnization.'

We believe that GBL Ingestion was notwidespread at the time of our study, but hasincreased since then

GBL has greater bioavaliabliity than GHBwhen given orally In the same dose GBL israpidly converted in the body by penpherallactonases to GHB within minutes.

Anotherchemlcal precursorto GHB IS 1,4­butanediol (1 ,4-BOl. sometimes called "pineneedle oil "21t is converted by alcohol dehy­drogenase to y-hydroxybutyraldehyde, thenby aldehyde dehydrogenase to GHB. WhereasGHB is acontrolled drug in several states, GBLand 1,4-BO are not yet classified as such, andboth drugs are readily available throughchemical supply catalogs

Rachel LChin, MDJo Ellen Dyer, PharmDKarl A Sporer, MDSan Francisco General Hospital1001 Potrero Avenue, Room lE21San Francisco, CA 9411047/8/97565

1 LoVecchIO F, Curry SC, Bagnasco T Butyrolactone­Induced central nervous system depreSSIOn after IngestIOn ofRenewTnent. a "dIetary supplement" N Engl J Med1998,339 847-848

2 Dyer jE. Galbo Mj, Andrews KM I,4-Butanedwl. "pIneneedle 011," overdose mlmlCS tOXIC profIle of GHB [abstractJelm TOXlCOl 1997.35554

More on the Ottawa KneeRules

To the Editor:

Clinical decision rules hold the promise toreduce health care costs while maintainingan optimal level of patient care The emer­gency medicine community and physiciansfrom other specialties have recognized theimportance ofthe contributions of Dr IanStiell and hiS colleagues toward the develop­ment of such rules to reduce extremity radlo­graphy.1.2

Atthe same time, It is Important for othercenters to independently validate the deci­sion rules that have been developed InOttawa The report by Seaberg et al3 raisessenous concerns about the sensitivity of theOttawa knee rules If any decision rule forextremity radiography is to be widely appli­cable, it must be broadly reproducible with100% sensitiVity. Unfortunately, Seaberg'sgroup found that the Ottawa knee rule was only97% senSitive forthe detection of fractures

We also recently reported aprospectivevalidation trial ofthe Ottawa knee rules In 351patients.4 Like Seaberg et ai, we found thatthat the rule developed by Dr Stiell missedseveral fractures 4The overall sensitivity ofthe Ottawa rule in our study was only 84.6%.

The reasons that the Ottawa rules wereless sensitive In these Independenttnals areunclear One particular concern that we havehad the opportunity to diSCUSS with Dr Stiell isthatthe "Intensive" instruction thatthephysicians received In Ottawa versus the othercenters may not have been uniform. It is essen­tial to future validation studies that Dr Stielloutline in detail his methods fortraining phYSI­cians In the use ofthe Ottawa knee rules

The work ofthe group In Pittsburgh suggeststhat clinicians should not use any of the cur­rent clinical deciSIOn rules for knee radiogra­phy as arigid standard that replaces clinicaljudgment altogether. The Pittsburgh rule mustbe Independentlyvalidated and refined Atthesame time, further validation tnals oftheOttawa knee rules that ensure conformity tothe phYSician instruction methods developedby Dr Stlell are warranted

Peter BRichman, MDDepartment of Emergency MedicineMorristown Memorial HospitalMorristown, NJ47/8/97566

1 Stlell IG, Greenberg GH, McKmght RD. et al DeCISIOnmles for the use of radIOgraphy In acute ankle InJunes

RefInement and prospectlve valIdatIOn JAMA1993.269 1I27-1I32

2 StlelllG. Greenberg GH, Wells GA, et al ProspectIvevaltdatIOn of a denswn mle for the u," of radIOgraphy In

acute kna InJunel JAMA 1996,275 611-6/5

3 Seaberg DC, realy DM Lukens T, et al MultIcentercompanson of two clInIcal dwsIOn mles tor the usc ofradIOgraphy In acute. hIgh-nsk knee InJun" Ann EmngMed 1998,32 8-13

4 Richman PRo McCuskey CF, Nashed AN. et alPerformance of two clInIcal deCISIOn mles for knee radlOg­raphy J Emcrg Mcd 1997,15 459-463

4 7 6 ANNALS OF EMERGENCY MEDICINE 334 APRIL 1999