In Part 1 of this post, I looked at the research surrounding the Cincinnati Prehospital Stroke Scale (CPSS), and found that 1) I wasn't particularly thrilled with the design of the tool 2) ditto the methodology of the derivation and validation studies, and 3) further studies demonstrated a wide range of sensitivity and specificity. Specificity is the big property for what I need; at the service I work for, we routinely fly stroke patients to our local stroke center. So I set out to find other stroke screening tools that have been published to see if there was something better. Here's what I found;
1) The Los Angeles Prehospital Stroke Screen (LAPSS). In 2000, the developers of the LAPSS published a study in Stroke validating their screening tool. Compared with the CPSS, the LAPSS includes history findings such as age, history of seizures/epilepsy, symptom duration, and ambulatory status. It excludes speech testing from the physical exam. Their study analyzed 206 patients who had an LAPSS form completed; 36 had a "target stroke". They found a sensitivity 91%, specificity 97%, PPV 86% and NPV 98%. Great numbers...but the original studies for the CPSS had similar numbers. I wanted some additional reporting.
2) The Miami Emergency Neurological Deficit (MEND) exam. This exam was developed as part of the Advanced Stroke Life Support course; I've not taken the course, so I'm unfamiliar with the methodology and application of this exam. It looks like it adds components of the NIHSS to the CPSS to expand the exam and provide some common ground with hospital-based clinicians. I did find a poster presentation of a study that looked at 51 airlifted patients who had a MEND exam performed in the field; they found that the MEND exam correlated with the NIHSS scale performed at the hospital 90.2% of the time. The participants of the study used the MEND exam, coupled with online medical consultation with a neurologist, to determine air transport. Of the 51 airlifted patients, 78.4% were diagnosed with CVA. The poster concluded that "The MEND exam is a valuable tool when assessing stroke patients in the field and determining the need for air transport". Again, I've not been trained on the MEND exam (although now I'm looking for a nearby ASLS course!), but I'm not sure I agree; in the study, online consultation with a neurologist seemed to be the mechanism for "pulling the trigger" on air transport. The MEND seems to be a great way to provide important information to hospital clinicians, but I can't find any research that spells out WHEN to call for air transport.
3) The Melbourne Ambulance Stroke Screen (MASS). Meanwhile, across the pond....some enterprising Aussie clinicians decided to combine the components of the CPSS and LAPSS and see if that improved diagnostic properties. They studied 100 patients who had a MASS completed, and compared the MASS to the CPSS and LAPSS. They found sensitivities of 90% vs. 95% vs. 78%, specificities of 74% vs. 56% vs. 85%, PPV of 90% vs. 85% vs. 93%, and NPV of 74% vs. 79% vs. 59%, all respectively. (Note that in this study, the LAPSS didn't work as well as the original validation study, but still pretty respectable).
In the end...I decided that the MASS was probably the best screening tool for my use. My next choice would be the LAPSS. But, I think it's important to remember the classic saying "When you've seen 1 EMS system.....you've seen 1 EMS system". We all have different needs for screening tools, diagnostics, and therapies. Rather than blindly accept what you were taught, look around for the best tools to stock your toolbox.
