With a pandemic raging, I hear a lot about testing. One problem is we don't have an adequate supply of test kits to screen for Covid-19. But another problem would arise even if we had enough kits to test everyone. To explain, I'll describe an example presented in Chance in Biology: Using Probability to Explore Nature, by Mark Denny and Steven Gaines. Their analysis was based on testing for HIV, but I'll recast the story in terms of the coronavirus. Suppose we have an accurate test for Covid-19. No test is perfect, so let's assume it's correct 99.5% of the time. In other words, its error rate is 0.5% (one error for every two hundred tests). Assume this error rate is the same for false positives and false negatives. Furthermore, assume Covid-19 is not prevalent, infecting only 0.1% of the population. I doubt this is a good assumption right now, when the virus seems to be infecting everyone, but I can imagine a time not too far in the future (a few weeks maybe, a few months probably) when the fraction of people having the virus is small. In a population of a million people, 1000 would have Covid-19 and 999,000 would not. First, consider what happens when you test the thousand that are infected. The test would come back positive for Covid-19 in 99.5% of the cases, so it would produce 995 true positives. The test would be in error and give a negative result 0.5% of the time, giving 5 false negatives (the test would say you don't have the disease when in fact you do). Next, consider the results from testing the 999,000 people who are not infected. Again, the test accuracy is 99.5%, so you would get a negative result (true negatives) for 994,005 people (0.995 times 999,000). You'd make a mistake 0.5% of the time, so you get false positives in 4995 cases (the test would say you have the disease when in fact you don't). Let's summarize: True Positives 995 False Positives 4,995 True Negatives 994,005 False Negatives 5 Now, suppose Michigan Governor Gretchen Whitmer (I'm a big fan of the governor) decides that—to prevent the virus from flaring up again—everyone will be tested; anyone who tests positive for Covid-19 must be quarantined, and anyone who tests negative is free to go wherever they please (restaurants, sporting events, movies... oh how I miss them!). Out of a million people, 5990 will test positive (995 + 4995). Of those, 4995 are mistakes (false positives). In other words, 83% of the people who are forced into quarantine are false positives; they don't have the disease, but the blasted test said they do and they must suffer for it. Only 17% of the quarantined people are infected. Is this acceptable? Maybe. We might decide as a state that it's worth it; we insist on quarantines, even if five out of six people forced into isolation are actually healthy. The needs of the many outweigh the needs of the few. Or, we might decide this is too high a price to pay; people are innocent until proven guilty, so to speak. This decision is not simple. Whitmer will have people mad at her regardless of what she does. But we must decide based on the facts. If the incidence of Covid-19 is 0.1%, and the accuracy of the test is 99.5%, then five out of six quarantined people will be false positives. That's how the math works. Denny and Gaines summarize it this way: “Although individual tests have a low chance of error, most individuals who are tested are not infected with [Covid-19]. Therefore, we are multiplying a small probability of false positives by a large number of uninfected individuals. Even a minute probability of false positives for individual tests can in this circumstance produce many more false positives than true positives. As long as the disease is rare, even a very accurate test of infection will not be able to accurately identify infected individuals in a random test.” I don't know the prevalence of Covid-19 or the accuracy of Covid-19 tests. The numbers for the coronavirus may be different than what I used in this example. My point is that even an accurate test can produce many false positives for a rare disease. That's an important insight, whether or not the numbers are accurate for our current plague. Chance in Biology is full of examples like this one. It's a good book (although I like Denny's Air and Water better). It's a useful supplement to Intermediate Physics for Medicine and Biology, providing all the probability you need to understand biological physics. Originally published on April 13, 2020 at https://hobbieroth.blogspot.com/2020/04/a-problem-with-testing.html
Many a time we fail to accept responsibility for our own lives. We forget that we drive ourselves to our own promised land. The most notable winners at some point encountered heartbreaking obstacles before they triumphed. They succeeded simply because they refused to be victims of circumstances. Certainly, nobody glows more than he who let the hurt go. Growing up just like any other normal kid I used to run around whenever I saw aeroplanes in the sky. At school I would say when I grow up I want to be a pilot. Can you imagine the excitement of the Wright brothers on the morning of that first flight? For the only boy in a family of four that would surely make a mother proud. Dreaming, after all, is a form of planning and only execution brings a glimmer of success. Things took a sudden twist in 2009 on the 21st of August when mother was involved in a fatal car accident along Seke road. Her spinal cord was left damaged and there was no hope that she could ever walk again. She was admitted at the Avenues hospital, where her recovery path seemed smooth. Within a few weeks, she was transferred to St Giles where she was to learn how to use a wheelchair. On one particular day, a doctor on night shift mistakenly handled her whilst she was in her sleep and she fell off the bed. Efforts to keep her alive were made but she died on her way to Parirenyatwa. When I received the news I realised that making mom happy was out of reach. The pain I felt made me want to save lives. I wanted to be a different doctor. Peace of mind became a fallen concept for me. I knew that for me to achieve this new found dream I had to work extra hard even if it meant that I had to starve whilst on books. It is during our hardest times that we discover our true taste and desire for success. I refused to conform to the dogmas of the society I lived in. Many a time young children who lose their mothers end up vagabonds. I constantly asked myself certain questions: Who am I around? What are they doing to me? What have they got me reading? What have they got me saying? Where do they have me going? What do they have me thinking? For some time I hated the so called street lingo ‘swagg'. Simply because I had an educational standard I was termed a nerd. I chose not to limit myself because of other limited imagination. I chose to leave a trail where there was no path than to further bare the usual pathway. I conquered my worst fears, failure. I joined medical school in august 2018. Driven by my personal statement: ‘TO BE THE LEAD PROVIDER OF INCLUSIVE QUALITY HEALTH. TO PROVIDE EQUITABLE, QUALITY, INCLUSIVE, RELEVANT AND COMPETENCE DRIVEN HEALTH SERVICES IN OUR BELOVED ZIMBABWE. I do not wish to be the wealthiest but certainly the most educated doctor of my generation with the aim of specializing later on as a neurosurgeon. Too many people wish to cross the fence and be where the grass is clean. I believe I am where I should be, all I need is to just water the grass I am standing on to make it green. The gods are different, the times are different but the underlying precepts of caring for the sick wherever or whoever they may remain the same. Having gone through some of the oath's for doctors I solemnly promised that I would to my best ability to serve humanity caring for the sick, promoting good health and alleviating pain and suffering. I now turn to my calling, promising to preserve its finest traditions, with the reward of long experience in the joy of healing. This promise is made freely and without coercion. Life is what we make it, always has been, always will be. The best way to predict your own future is to create it and live to it. It is under the greatest adversity that there exists the greatest potential for doing well.
It all started when I finished high school. At that time, I did not have a concrete plan of what I should do ; I just studied well so i can study medicine in the UK. When I look back now, lots of things led to me being here. In 2015, after graduating high school I started contacting universities in UK ,but to no avail and time just flew by; one year passed while trying in all possible ways to study medicine there until a staff member of a certain university told me frankly it's hard to be accepted in medicine in UK and it was extremely expensive for me as well .A year passed by which was devastating because I had this thought that I should apply right after high school like all other students ingrained in my mind. I started to think differently that I wanted to be satisfied with what I am doing, feeling fulfillment by helping others. Something that by the end of my life makes me think like ‘yes I've spent 100000 hours doing this job' so I decided to study medicine in turkey and I became even more confident about what I want; I applied to a university and was accepted ,but then my father had a financial problem so later by the help of my mother I applied in another university which i believe now is better. I was the type of kid who was very dependent on her parents' money to study in school and university; don't get me wrong I am not spoiled or anything i was just raised like that; i was young after all and I was never pushed to the edge as now to start working and earning my own money ,to stand on my own two legs. I always wanted to be independent financially ,but not like this; I had a robotic way of thinking of getting my degree first then start to depend on myself. After graduating from school, I took two gap years, two years of anyone's most precious time “youth”. When I finally started university I was 21 by then, the emotions I went through those two years were horrible; I was really depressed seeing everyone from school going to universities except me; it left a huge impact on my personality, for some people this might look trivial ,but for me it was my future; it was everything on stake simply because there was no other way for me to study medicine unless i travel abroad and to study medicine in a private university which is not cheap. I started thinking will i even start studying in a university; I did not want to study in my country because that would mean I'll just study business and stay in my shell. I wanted to travel and experience everything that comes with traveling from depending solely on my self to having new friends, new encounters, meeting people with different views on life from different cultures which eventually happened. In my teens, I used to watch lots of Turkish dramas which made me want to learn Turkish language and go to Turkey as a tourist ,but never thought of coming here as a student. In the two years, I had taken a Turkish language course; it was a nice experience to learn Turkish which helped me later on when I decided to go to Turkey. In 2017, I finally started university and yes my financial problem was not yet solved not even till now, but somehow the ship sailed although I still have debts to my university. Now I should be in 3rd year, but that's still vague because my financial problem got worse; it's this year that I started to think out of the box when the pressure inside was too much for me to handle. It's these kinds of situations that actually make us who we are and know how to tackle our problems. This summer because of the pressure of the makeup exam which if I failed would mean I lost another year and the money problem; I had decided to start working already.One thing led to the other; in my gap year I used to read comics and novels so I thought why not start writing and publishing a novel online myself; I started entering contests such as this one and I also started my own comic with a collaboration with a comic artist which I hope will be published soon. Yes, I accept what is happening with me, but that doesn't mean I should give up; It only means I should try harder until I get that degree. Indeed moving to another country now after I settled here is not easy furthermore it was hard for me to be emotionally stable because as much as I wanted to travel abroad, in my first year reality hit me hard and I started missing my family and I even regretted coming to Turkey ; I was very depressed, but that all subsided now; I became more independent; I have friends who stood beside me and made me feel as if they were my second family here. As I am writing this ; it strikes me how much I've changed through these last couple of years into a mature, strong-willed woman from just an indecisive high school girl, so if someone is reading this who went through a bad experience don't worry, you're not alone and always remember it's all for your best because believe me you will flourish into something really beautiful and remember everything happens for a reason.
She came in early one morning, comatose, silently pale, her breath rising and falling together with the ventilator, hooked to a hundred machines, monitors blinking, real time data, IV pumps lining the pole like birds on a wire. Day before yesterday she was trimming hedges, climbing ladders, raking the yard, making plans for Thanksgiving. Day before yesterday she was whole, complete, functional, capable, making memories, living life, combing her hair, telling stories with friends. Then, without warning, some weak spot gave way in her brain, some vessel decided enough was enough and blood began to spread through the white matter of memories, of conscious thought and decision, an evil red flood obliterating hopes and dreams. The diagnosis is grim, cerebral hemorrhage, prognosis uncertain. The surgeons place a drain, straight down into the ventricles, leaving an aerial-like appendage sticking out of her skull, pointing straight up, a fiber-optic wire and a tube emanating from within, a human technological hybrid. The wire is hooked to a monitor that gives continuous readings of pressures inside the skull; the tube drains fluid once it reaches a certain level. Our goal is to keep pressure down, save the brain, conserve whatever is left inside, preserve life, return the trimmer to the hedge, the climber to the ladder, the raker to the yard. Her family comes in, some in shock, some realistic, eyes red, weeping, sharing memories. They can't believe they're here, can't believe she's here, can't believe she's on life support, overwhelmed by the blinking lights, the soft glow of machines and monitors. I try to explain, gently, the methods to our madness, the small pole sticking out of mother's skull, the appendages here and there, the lines and tubes. They ask me what I think, will she make it, will she ever be back to normal? I shrug slowly, turn my face, tell them the truth, we're doing everything we can, but chances are slim she'll come out of this. Eyes meet, eyes fill, they turn away, sit down heavily, not believing. Then another figure steps inside. Another daughter. This is the special one they whisper to me, the one the patient worried about, prayed and lived for, the black sheep of the family, history of depression, anxiety, no money, empty dreams. She sits beside her mother, lays her head on the bedrail and begins to cry, great sobs from deep inside, a million memories pouring over her heart like white-water over rugged stone. That's when I notice the monitor, the one measuring the pressure in the brain. The numbers start to rise, as the daughter hangs on to mother, as daughter pours out her soul, her tears falling on the sheet. The number keeps rising until the alarm goes off. The daughter looks up, leans back, and takes a deep breath. The numbers on the monitor begin to fall, to go back to normal. The daughter leans forward again, cries softly, whispering, reliving old times, sharing memories, saying please don't go, I love you, I need you, I can't do it without you. And the pressures begin to rise again, again the alarm sounds. I stand in a trance, spellbound, unbelieving, in awe. Something deep inside this coma-stricken mother is responding to the mournful sound of her beloved, her grief stricken daughter, flesh of her flesh. Doctors and surgeons, nurses and therapists, we all try our art, apply the treatment, order the interventions, but nothing reaches, no response, nary a nod. But somewhere in here we missed the soul and the soul connected, somehow; connected beyond me, connected beyond all of us, connected with the soul of her daughter. Hours later as the black sheep continues to whisper and to weep, the mother passes from this life into the next. As the monitors cease to flash and blink, I walk from the darkened room, pensive, sober, thoughtful. I like to think that for a moment the soul in the body of the sick and dying mother met with the soul of her daughter and that they talked, shared a sweet communion, and had the chance to say goodbye.
It's kind of funny thing for me to hold a pen right now and to write down something that is not connected to my study subjects. Last time I wrote an essay in 11 form. It was usually about some books that I've read or just some typical school themes. Now I'm on the 3 course of medical university in Ukraine. And I'm free to write everything that I want. But here is a question. What is the most interesting topic for me? What I want to tell about. That is really complicated. I would love to tell about my exciting hobbies, but I don't actually have any. I don't play any instruments, unbelievably bad at chess and don't really go in for sports. Sounds a little boring, I know. But I've got one thing that I'm really interested in. It is learning languages. Especially English. Not sure that I can call it a “hobby”, but at least it's better than nothing, right? I love watching serials and movies in English (with eng subtitles of cause I'm still not such a good speaker as I dream to be). I also read some books in original as I think that there is no translation which could reproduce the real meaning of the author's words. Not for so long time ago I used to think that my future profession would be connected to learning English. I dreamed to be a translator or even some ambassador. But my parents convinced me to choose medicine as it is more achievable to me. The whole first course I was regretting about this choice. The only thing I liked was English. And in my university there was only 1 lesson of English per week. One, Carl! The second course didn't actually differ. But this year I found out that there are a lot of people like me in my university. People who love English and would like to study it. And then I've decided to make an English club for these people. It's like some informal meetings after lessons. I usually prepare some presentations, videos and games for every time. At first it was really scary for me to imagine myself talking in front of an auditory like a lector. But everything has changed after the first lesson. It's unbelievable feeling to share my experience with other people and to see the way they like it. I really do my best for these lessons and I feel such a pleasure when I see that people appreciate it. My faculty is dentistry so I usually try to connect my themes with some dental issues. For example, we learn about caries and other diseases, teach each other how to communicate with our patients in English and so on. My students ( if I can call them like that 😄) like it and this is the most important part for me. Everybody is free to say everything he wants and nobody is ashamed to ask for a help with some grammar or to say “I don't understand”. It's OK. Because that's what we are doing. Studying! I'm glad to explain things as many times as person needs to be sure that he/she has got everything on well. Practice makes perfect! I don't know what my life is going to be in 2 years, but the only thing I'm sure about is that I want to connect my future with English. Studying or teaching? Both! Because I'm convinced that you can never be a good teacher if you don't improve yourself. Am I sure that my dreams will come true? No. But nothing is impossible for a willing heart. Right?☺️