LMP301 2014 Lecture 1.pdf

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Laboratory Medicine and Pathobiology
Kenneth Yip

  Lecture  1  –  Introduction  to  the  Biochemistry  of  Human  Disease     What  is  Disease?   -­‐ Dorland’s  Medical  Dictionary :  definite  sickness  having  a  characteristic  train  of  symptoms   -­‐ In  Boyd’s  Introduction  to  the  Study  of  Disease:  a  disease  is  the  pattern  of  response  of  a  living  organism  to  some   form  of  injury   -­‐ An  injury  can  be  starvation,  a  poisoning,  an  infection,  stress  from  crowding,  depression  from  loss  or  failure,  a   trauma,  and  much  more     Definitive  Diagnosis   -­‐ usually  requires  objective  evidence  of  the  pathologic  process   -­‐ ex.   à  demonstration  of  specific  biochemical  abnormality   à  visualization  of  a  tumor  by  ultrasound  imaging   à  finding  an  inflamed  appendix  at  surgery  à  appendicitis  –  inflamed  appendix  during  surgery   à  isolation  of  bacillus/virus  à  infection  by  bacteria   à  location  of  a  lesion  in  the  tissue  by  biopsy  (cancer  or  lesion)   à  take  close  look  under  microscope  will  see  lesion   -­‐ not  just  looking  at  physical  appearance,  but  very  specific  disease  part  of  the  body     Medical  Laboratory  Services   -­‐ pathology  (anatomic),  includes:   à  histology  (tissues)  and  cytology  (cells)  à  often  microscopic   -­‐ hematology,  includes:   à  diseases  of  the  blood,  blood  transfusion  medicine ,  and  immunology   -­‐ microbiology,  includes:   à  various  infectious  agents:  bacteriology,  virology,  parasitology,  mycology   -­‐ biochemistry,  or  clinical  chemistry   -­‐ genetics,  includes:   à  molecular  genetics  –  changes  in  genes     Why  Biochemical  Testing?   -­‐ Use  this  test  before  considering  other  tests   -­‐ biochemistry  analyzes  chemical  markers  found  in  cells  and  fluids  (e.g.  blood,  serum,  urine,  etc.)  à  easy  to  obtain   -­‐ less  painful,  relatively  non-­‐invasive  and  safe  compared  to  biopsy  (removes  tissues)   -­‐ small  amount  sample  is  often  enough  for  analysis   -­‐ many  tests  (“assays”)  have  been  developed  to  a  high  degree  of  sensitivity  and  accuracy,  as  well  as  fast  speed  of   analysis  à  fast  and  accurate  speed  of  analysis     Objectives  of  Lab  Medicine     1) help  define  as  objectively  as  possible  health  and  disease   2) help  predict  the  course  of  a  disease  (what  is  your  chance  of  survival?)   3) monitor  the  effectiveness  of  treatment  (are  you  getting  better?)   4) seek  for  underlying  cause  of  disease   5) to  screen  for  unsuspected  disease   Use  of  Biochemical  Testing   • Diagnosis:  does  the  glucose  level  indicate  diabetes   • Prognosis:  is  the  cancer  curable?   • Monitoring:  has  enough  of  medication  been  given?  –  monitor  drug  level   • Etiology:  what  is  the  cause  of  the  kidney  disease?  –  kidney  disease  has  numerous  causes,  lab  tests  can  identify   which  one  is  the  reason   • Screening:  what  is  risk  of  having  a  hear t  attack  in  CVD  in  the  future?     Social  Role  of  Laboratories  –  impact  of  disease  on  society   -­‐ mortality:  disease  that  causes  death  or  reduces  life  expectancy  –  want  to  live  longer   -­‐ morbidity:  disease  that  impairs  the  well  being  and  productivity  of  an  individual  –  may  not  die,  but  cannot  move   around,  blindness,  etc.   World  Wide  Mortality   -­‐ in  Western:  main  killers  (2  highest)  are  cardiovascular  diseases       -­‐ ischemic  heart  disease  causes  7.1  million  deaths,  then  its  cerebrovascular  disease  (5.7  mill),  th en  its  lower   respiratory  infections  (4.2  mill)   -­‐ however,  in  developing  countries,  death  is  mostly  due  to  infectious  diseases  (lungs,  digestive  system,  HIV,  TB,  etc.)   -­‐ in  Canada,  the  main  cause  of  death  is  2009  was  cancer  (30%),  then  cerebrovascular  disease  ( Stroke  –  21%),  then   its  chronic  lower  respiratory  disease  (6%)   -­‐ demographics  can  help  understand  the  disease  and  conditions  they  are  prone  to   -­‐ in  Ontario,  the  main  cause  of  hospitalization  are:   à  young  people:  childbirth  and  accidents   à  middle  aged:  cardiac   disease  and  strokes   à  elderly:  cardiac,  stroke,  cancer,  respiratory,  mental  diseases     Incidence  vs.  Prevalence  à  these  two  terms  are  from  epidemiology  (disease  of  population)   -­‐ the  prevalence  of  disease  is  the  number  of  cases  of  disease  in  a  given  population  à  high  prevalence  =  high   probability  of  the  disease   -­‐ the  incidence  of  disease  can  be  calculated  as  the   number  of  new  cases/unit  of  time  à  number  of  newly   diagnosed  disease  in  that  year     Endemic  vs.  Epidemic   -­‐ endemic  is  when  most  of  the  population  has  the  disease  (common)  à  HIV/AIDS  in  other  countries   are  high   compared  to  ours  à  their  prevalence  is  high   -­‐ epidemic  refers  to  widespread  occurrence  in  a  population  where  it  is  rare  (ex.  Flu   –  fairly  low  in  number  unless   there  is  a  breakout  and  passed  to  many  indi viduals     Disease  Classifications   -­‐ anatomical  (location  where  its  found):  e.g.  cardiac  disease   -­‐ physiological  (related  to  particular  process):  e.g.  endocrine  disease   -­‐ systemic:  involves  many  systems  or  the  whole  body  (e.g.  infections)  -­‐  widespread   -­‐ etiology:  classifying  it  by  the  cause  of  disease   Common  Classifications  è   -­‐ Flu?  Infections,  inflammatory,  respiratory  disease   -­‐ Leukemia?  Can  be  hereditary,  cancer  of  blood,  hematologic  disease   (blood  disease),  genetic  disease   -­‐ Iron  overdose  from  multi-­‐vitamins?  Could  be  nutritional,  toxicology,   iron  over  dose  common  in  children  from  child’s  supplements       Hereditary   -­‐ Passed  from  parent  to  offspring   -­‐ Garrod  (1909)  introduced  the  concept  of   inborn  errors  of  metabolism  =  inherit  trait  that  leads  to  failure  of  function   -­‐ Inheritance  leads  to  failure  of  function   -­‐ Identified  from  studies  of  individual  gene  analysis  to  human  population  studies   -­‐ Often  early  but  can  occur  at  any  age   -­‐ Examples:  sickle  cell  anemia     Congenital   -­‐ refers  to  disease  appearing  at  birth   -­‐ not  always  hereditary   -­‐ e.g.  maternal  measles,  fetal  alcohol  syndrome     Injury   -­‐ trauma  or  mechanical  injury  can  lead  to  necrosis  (death  of  tissue)  or  loss  of  tissue   -­‐ Physical  injury:  direct  trauma  -­‐  leads  to  disease  conditions  caused  by  mechanical  stress,  burns,  heart  stroke,  fros t   bite,  electrical  hazards,  radiation  exposure,  and  atmospheric  pressure  injuries   -­‐ Chemical  injury:  the  study  of  this  is  toxicology.  Injury  from  drugs,  toxins,  or  other  chemicals  à  damage  to   tissue/organs.  Poisoning  could  be  accidental,  suicide,  homicide,  or  from  industrial  hazards  (damage  to   tissue/organ  à  environmental  –  pick  up  from  environment)     Infections   -­‐ most  common  are  bacterial  or  viral       -­‐ epidemiology  is  the  observation  of  the  occurrence  of  disease  in  populations;  pioneered  by  the  efforts  to  control   infectious  diseases   -­‐ some  useful  terms:  prevalence  and  incidence,  endemic  and  epidemic     Inflammation   -­‐ most  infections  produce  inflammation  but  not  all  inflam mation  is  due  to  infection   -­‐ symptoms  include  fever,  chills,  and   leukocytosis  (production  of  WBC  to  fight  off  infections)   -­‐ controlled  with  drugs  even  if  mechanism  of  injury  or  the  antigenic  stimulus  is  not  known   à  may  not  know  definitive  diagnosis  (exact  reas on  why  you  have  inflammation  symptoms),  but  if  you   start   treating  it  with  aspirin  or  steroid  can  reduce  severity  of  disease  (might  not  cure  it,  but  can  treat  it)   -­‐ autoimmune  diseases  =  rejection  of  self  à  immune  system  attacks  own  tissues   à  immune  system  causes  injury  to  normally  functional  cells   à  not  an  infection,  but  can  lead  to  inflammation  (if   inflammation  goes  on  and  damages  cells,  you’ll  have  a  disease  process  going  on)     Vascular   -­‐ vessels  (circulatory  system)   -­‐ atherosclerosis  (deposition  of  fats  in  vessels)  or  arteriosclerosis  (hardening  of  arteries)  are  likely  the  most   common  disease  of  the  Western  world   -­‐ atherosclerosis  à  plaque  rupture  +  thrombosis  à  ischemia  à  tissue  anoxia  à  damage  and  cell  death   -­‐ may  involve  inherited  or  acquired  factors   -­‐ e.g.  increased  incidence  in  people  with  hypertension,  hypercholesterolemia,  diabetes  mellitus,  obesity,  or   those   who  smoke     Metabolic  and  Nutritional   -­‐ nutritional  disorders  are  due  to  diet   -­‐ most  common  world  wide  is  inadequate  number  of  calories  in  the  diet  (poor  food  supply  and  development)   -­‐ in  the  West,  we  have  too  much  food  but  of  poor  quality  ( from  processing  à  contributes  to  obesity)   -­‐ metabolic  disorders  result  in  abnormal  production  of  enzymes,  hormones,  or  secretory  products   -­‐ could  be  defect  in  chain  where  everythin g  after  that  point  is  too  low   -­‐ could  get  build  up  of  metabolites  and  could  lead  to  disease  process   -­‐ often  hereditary  but  some  may  be  acquired  (diet  too  high  in  fat,  too  low  in  protein)     Tumours   -­‐ diseases  of  abnormal  growth,   neoplasia  (new  growth)  leading  to  tumours   -­‐ growth  occupies  space  and  may  obstruct  or  compress  other  tissues  (mass  effect)  and  so  lead  to  disease   -­‐ some  tumours  secrete  hormone-­‐like  chemicals  which  disrupt  body  functions  à  excess  production  of  a  hormone   à   disrupts  body   -­‐ cancer  refers  to  malignant  neoplasms,  often  with  the  ability  to   spread  (metastasize  –  when  tumour  cells  come  off   the  main  one,  into  circulation,  and  goes  to  other  sites)     -­‐ iatrogenic  disorders  are  caused  by  physicians     o e.g.  the  over  prescription  of  drugs  (caused  by  bad  decisions)   -­‐ psychological  disorders  could  include  depression -­‐related  changes  in  body  chemistry   -­‐ idiopathic  disease  are  those  with  an  unknown  cause  (can  be  harmful  or  harmless)     Two  Reasons  why  Lab  Tests  are  Ordered   1) for  diagnosis  of  disease   2) for  management  of  illness  or  health     Purpose  of  a  Diagnostic  Testing   -­‐ to  screen  for  disease  without  symptoms   -­‐ “screening”  seeks  to  find  hidden  disease  in  a  population  deemed  to  be  healthy   à  screens  disease  where  no   symptoms  are  present   -­‐ OR  to  confirm  a  disease  that  there  is  some  evidence  for   -­‐ OR  to  exclude  a  disease  that  is  possible  but  not  likely   o to  confirm  or  exclude  a  disease   Examples   -­‐ screening   o heart  disease  à  cholesterol       o prostate  cancer  à  PSA  (Screens  for  prostate  cancer)   -­‐ diagnosis   o myocardial  infarction  (heart  attack)   à  troponin  (marker  -­‐  used  to  confirm  that  a  heart  attack  took  place)   o diabetes  à  glucose   -­‐ exclusion  test   o pregnancy  à  chronic  gonadotropin   à  harmful  to  give  female  an  x -­‐ray  that  might  be  pregnant,  so  before  x -­‐ray,  make  sure  there  is  no   pregnancy   Purpose  of  Management  Testing   -­‐ to  monitor  the  treatment  of  disease   -­‐ OR  to  follow  the  course  of  the  disease  à  make  sure  disease  is  not  coming  back   -­‐ OR  to  predict  what  is  likely  to  happen  to  the  patient  (i.e.  prognosis)   -­‐ ex.     • Is  the  dose  of  drug  within  the  effective  range?  Drug  dosin g  is  done  to  monitor  amount  of  drugs  in  body   • Is  there  recurrence  of  the  cancer?  biochemical  marker  might  show  up  if  reoccuring   à  cancer  treated,  want  to  make  sure  it  doesn’t  come  back,  so  want  to  check  if  there  is  a  biochemical  marker   that  shows  up  if  it  comes  back      Other  Reasons  for  Testing   -­‐ for  curiosity  (pure  research)   -­‐ to  practice  “scientific  medicine”  à  test  things  certain  time….  PSP,  PAP,  etc.  (follows  guidelines,  show  check  this  and   that  once/twice  a  year,  etc.)   -­‐ to  follow  tradition  (bad  reason)   -­‐ to  avoid  litigation  (there  are  some  legal  requirements  for  some  tests  to  be  done  prior  to  surgery)   -­‐ to  make  money  (for  ex.  Patient  must  make  another  billable  visit  to  the  office  for  treatment  or  advice  following  the   laboratory  result)     Lab  Reimbursement  in  Ontario   -­‐ schedule  of  Laboratory  Services  funded  by  the  MOHLTC   -­‐ lab  areas  generally  divided  into:   à  clinical  biochemistry   à  hematology   à  immunology  (often  part  of  biochemistry)   à  microbiology  (including  virology  and  parasitology)   à  anatomic  pathology     -­‐ in  hospital  laboratories,  biochemistry  and  hematology  laboratories  usually  have  an  STAT  service  and  a   Routine/”Core”  Laboratory.  Large  center s  would  have  specialized  lab  testing     Test  Menu  Considerations   -­‐ categories  of  test  menus   à  “STAT”  tests   à  routine  tests   à  specialty  tests   -­‐ considerations  for  test  availability   à  turn-­‐around  time  (TAT)  –  how  quickly  you  need  the  result   à  Cost  control   à  technical  expertise  –  training  and  experience   à  clinical  need     Types  of  Markers   Some  type  of  molecule/analyte  of  interest,  which  tells  us  a  particular  disease/diseases   1) Physiological  Markers   o Analytes  which  are  monitored  to  asses  normal  function  (constituen ts  in  the  body,  like  electrolytes,  that  are   normally  around)   o Tightly  controlled  by  body  (within  a  certain  range)   o Under  normal  physiological  response  (stress   –ex.  Disease),  body  will  restore  the  balance   o Can  give  specific  information  about  organs  (ex.  Albumi n  and  protein  tells  us  about  the  kidney)   o Injury  or  disease  may  alter  the  balance;  body  may  or  may  not  be  able  to  compensate   à  once  its  outside  the  normal  range,  it  can  be  an  indication  of  disease       o E.g.  electrolytes,  blood  gases,  pH,  glucose,  protein   2) Disease  Markers   o Analytes  which  are  monitor
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