DIAGNOSIS OF SEPTICEMIA

Causative organisms:

(Mention those bacteria that you are well-conversant with)

Gram negative cocci – meningococci, gonococci, hemophilus
Gram negative bacilli – Salmonella typhi, EIEC, almost all causes of UTI, Infective endocarditis (including HACEK organisms), meningitis.
Gram positive organisms (rare) – Streptococcus, Staphylococcus, Pneumococcus, almost all organisms that cause osteomyelitis and pneumonia.

Material for diagnosis:

Venous blood – 3 samples at 0, 30 and 90 min intervals from admission
Urine
CSF (if features of meningeal irritation are present)
Swab from suspected skin lesion


Steps of diagnosis:
Exams and Tests

Physical examination may show:

Low blood pressure
Low body temperature or fever
Signs of associated disease (such as meningitis, epiglottitis, pneumonia, or cellulitis)

Tests that can confirm infection include:
Blood culture
Urine culture
CSF culture
Culture of any suspect skin lesion
CBC
Platelet count
Clotting studies
PT
PTT
Fibrinogen levels
Blood gases

BLOOD CULTURE
A minimum of 10 ml of blood is taken through venipuncture and injected into two or more "blood bottles" with specific media for aerobic and anaerobic organisms.
Care needs to be taken that the bottles are not contaminated with bacteria from staff members or other patients. To that end, the patient's skin is rubbed or sprayed with denaturated alcohol and betadine applied to the sampling site. Sterile gloves should be used to minimize contamination.
To maximise the diagnostic yield of blood cultures multiple sets of cultures (each set consisting of aerobic & anaerobic vials filled with 3-10 mL) may be ordered by medical staff.
Set 1= L. antecubital fossa at 0 minutes
Set 2= R. antecubital fossa at 30 minutes
Set 3= L. or R. antecubital fossa at 90 minutes
Ordering multiple sets of cultures increases the probability of discovering a pathogenic organism in the blood and reduces the probability of having a positive culture due to skin contaminants.
After inoculating the culture vials on the hospital floor, they are sent to the microbiology lab clinical pathology department. Here the cultures are entered into a blood culture machine, which keeps the samples at body temperature. The blood culture instrument reports positive blood cultures (cultures with bacteria present, thus indicating the patient is "septic") by monitoring carbon dioxide levels produced by bacteria in the vials via fluorescence detected by a light emitting diode (LED). Most cultures are monitored for 5-days, after which, if the vials are negative, they are removed.
If a vial is positive, a microbiologist will perform a Gram Stain on the blood for a rapid, general ID of the bacteria, which they will report to the attending physician of the septic patient. The blood is also subcultured or "Subed" onto agar plates to isolate the pathogenic organism for culture and suceptability testing, which takes up to 3 days time. This culture & sensitivity (C&S) process IDs the species of bacteria. Antibiotic sensitivities are then assessed on the isolate to inform clinicians on appropriate antibiotics for treatment.
Some guidelines for infective endocarditis recommend taking up to 6 sets of blood for culture (around 60 ml).

URINE EXAMINATION:
(Summarize the Laboratory diagnosis for UTI)
CSF EXAMINATION:
(Summarize the Laboratory diagnosis of Meningitis)

ROUTINE EXAMINATIONS
CBC - may show neutrophilia (enteric fever may show neutropenia)
Platelet count - may decrease following DIC
Clotting studies
PT - may rise following DIC r hepatocellular failure
PTT - may rise in DIC
Fibrinogen levels – may be low in DIC
FDP – may rise in DIC
Blood gases – may be abnormal in respiratory failure (raised pCO2 and low pO2)

CONCLUSION:
Based on the above investigations we can reach a diagnosis of septicemia.

Approach to pathological diagnosis of diseases

How do I approach a question on laboratory diagnosis in pathology?

Dear friends,

As part of your second professional examination, all of you will face a compulsory question on laboratory diagnosis of a particular condition. Here is a basic guide to how to approach such a question.

The questions on laboratory diagnosis may be placed in two ways. Study the following questions carefully:

1. How do you approach to diagnose acute leukemia in the laboratory?

2. A 17 yr boy came to the outdoor with complaints of fever and nodular swellings over neck. On examination, he had marked pallor. How do you approach to diagnose the case in the laboratory?

A quick look will reveal that the approaches of the two questions are different. The first question points to a specific diagnosis and asks about the relevant laboratory investigations needed to establish the diagnosis. The second question gives you a constellation of symptoms and signs and asks you to make a clinico-pathological diagnosis.

Let us first pick up the second question and try to solve it. For all practical purpose, your answer can be divided into the following parts:

• Case summary
• Provisional diagnosis
• Differential diagnosis
• Approach to diagnosis
  

Case summary:

This means you summarise the history and clinical features mentioned in the question in a logical manner so that it can point to a specific diagnosis.

For Q.2 it can be written as follows –

History: a boy aged 17 yrs came with a chief complaint of – a) fever, b) nodular swellings over neck.

Physical examination: marked pallor


Provisional diagnosis (PD):

This means, you write down the most appropriate diagnosis that matches with the given symptoms. The appropriateness will depend on –

• The prevalence of the disease. The commoner the disease more is the chance of the person suffering from it. Remember, rare diagnoses are rarely correct.
• The disease that you choose as your PD should logically explain all the symptoms and signs mentioned in the question.
• Your PD can be different from your friend’s PD. There is no rule of thumb that all PD has to be the same.
  For examination purpose, try to choose the PD from the diseases that are important in your syllabus. This is because examiners will expect you to answer from the chapters you have read. Moreover, the diseases that you read in your syllabus are also the commoner diseases.

For Q2, I can write my provisional diagnosis as follows:

Provisional diagnosis: Acute leukemia, probably ALL


Differential diagnoses (DD):

This means, you list all the diseases (or their complications) that can mimic the signs and symptoms of your PD. Please remember that this is the most important part of your answer. Follow these simple rules to find out the probable DDs:

• Keep your mind open to all possibilities (including relatively rare diagnosis) while searching for DD
  Search for the diseases systemically, i.e. follow a pattern of going through different systems of the body. This will ensure that you never miss a DD
• You can also include complications of a primary disease as a DD
• Remember, your DD can be someone else’s PD!

As for example, let me list the DDs for Q2.

Differential diagnoses:

a) Hematological:

1. Acute lymphatic leukaemia ( your PD is always your first DD)
2. Juvenile CML (in blast crisis phase)
3. Hodgkin’s lymphoma
4. Infectious mononucleosis

b) Respiratory:

1. Pulmonary tuberculosis ( anemia is due to chronic disease)

c) Multisystemic:

1. Septicemia
2. Metastatic carcinoma ( with Lymph Node and Bone Marrow metastasis)


This is how you list your DDs.

Now you might wonder why at all should we bother about the DDs? Because, we need to investigate only when there is some confusion in the diagnosis and we want to rule out the other causes. If we are already sure about a single diagnosis, there will be no need to investigate at all!

Differential diagnosis is a scientific approach by which we can reach at a single diagnosis by clinical and laboratory tests (very much like testing for the acid and basic radicals of an unknown salt in the chemistry lab).


Approach to diagnosis:

This can be done by following four simple steps:

1.Find out the systems of the body that your DDs cover
2.Note down the routine investigations that you do for each systems
3.Note down the specific or confirmatory diagnosis for each of the DDs
4.Now make a chart with the left-most column reading “steps of diagnosis”, and the rest of the columns dedicated to each individual disease. Point down the list of all investigations that you have listed in the above steps. Write down the findings of each disease against each point. If the test is in no way related to the disease, you can expect the finding to be normal. Mention if the finding may change with a complication.

For Q.2, the left column may include the following points:

1) History

2) Clinical features

3) Routine blood examination
· Hb
· TLC
· DLC
· Platelets
· Reticulocytes
· Abnormal cells

4) Bone marrow examination
· Cellurarity
· Nature of myelopoiesis
· Nature of erythropoiesis
· M:E ratio
· Megakaryocytes
· Plasma cells
· Abnormal cells/ parasites

5) Biopsy from the nodular tissue
· HE stain

6) FNAC from nodular tissue
· Pap stain
· Gram stain
· Acid fast stain

7) Blood culture

8) Chest X ray

9) Abdominal CT scan/ USG (to rule out occult neoplasm)



Now in case of Q.1, where the question is straight and simple, (Lab diagnosis of Acute leukemia), follow these steps:

1.List all the pathological types of the disease ( In this case, ALL and AML)
2.Jot out the points for diagnosis as before
3.Jot out the points for diagnosis of complications
4.Now make a chart with the left-most column reading “steps of diagnosis”, and the rest of the columns dedicated to each type. Point down the list of all investigations that you have listed. Write down the findings of each disease against each point. If the test is in no way related to the disease, you can expect the finding to be normal. Mention if the finding may change with a complication.


So, here you go… try and write the entire approach yourselves, and get back to us if you face any problem. You can also email your completed answers to tirthankar82@yahoo.co.in which we can publish with your names.

Till then, take care.

Cheers!