Hematology-Oncology Calculators

What haematology-oncology covers, and the clinical questions these tools answer

Haematology is the study of blood, bone marrow and coagulation. It covers anaemias, platelet disorders, clotting and bleeding disorders, leukaemias, lymphomas, myeloma and transfusion medicine. Oncology overlaps heavily with it: the staging, prognosis and treatment tolerance of cancers, both blood cancers and solid tumours, where chemotherapy brings its own haematologic risks. The calculators in this library answer the practical questions that recur across both fields.

The simplest tools are also the most used. The absolute neutrophil count (ANC) calculator converts a routine full blood count into the single number that defines neutropenia and its severity: counts below 500 cells per microlitre mark severe neutropenia, the threshold at which infection risk climbs steeply and fever becomes an emergency. The absolute lymphocyte count supports the workup of lymphopenia and immune dysfunction. The reticulocyte production index (RPI) answers a different bedside question in anaemia: is the bone marrow responding? An RPI above 2 suggests an adequate marrow response and points toward blood loss or haemolysis, while a low RPI points toward underproduction, such as iron deficiency, B12 or folate deficiency, or marrow failure.

Coagulation questions are covered by the 4Ts score for heparin-induced thrombocytopenia (HIT), which estimates the pre-test probability of HIT from the degree and timing of the platelet fall, the presence of thrombosis, and alternative explanations. It is designed to be used before laboratory confirmation, because waiting for results while continuing heparin can be dangerous. The Khorana score addresses the opposite risk: venous thromboembolism in ambulatory cancer patients starting chemotherapy, identifying who is at high enough risk that thromboprophylaxis is worth discussing. The revised Geneva score estimates the pre-test probability of pulmonary embolism to guide the choice between D-dimer testing and CT pulmonary angiography, while the PESI score stratifies 30-day mortality in confirmed PE, helping identify low-risk patients who may be treated as outpatients.

Prognosis and treatment planning are served by several cancer-specific systems. The International Prognostic Index (IPI) combines five clinical factors to stratify aggressive non-Hodgkin lymphoma into risk groups that inform discussions about treatment intensity. The ISS and revised ISS stage multiple myeloma using beta-2 microglobulin and albumin, with the revised version adding LDH and high-risk cytogenetics for finer prognostic detail. The PLASMIC score estimates the probability of severe ADAMTS13 deficiency in suspected thrombotic thrombocytopenic purpura (TTP), supporting the decision to start plasma exchange urgently rather than waiting for confirmatory testing. The MASCC risk index stratifies febrile neutropenia: a score of 21 or above identifies low-risk patients who can often be managed as outpatients with oral antibiotics, while lower scores point to inpatient care. Finally, the Charlson comorbidity index weights coexisting conditions to estimate longer-term survival, a useful input when judging whether a patient is likely to tolerate intensive therapy.

When clinicians and students reach for these calculators

In the emergency department these tools support time-critical triage. Febrile neutropenia is scored with MASCC on arrival; suspected pulmonary embolism is worked through the revised Geneva score before imaging is ordered; a falling platelet count in a heparinised patient triggers the 4Ts; and the combination of thrombocytopenia with microangiopathic haemolysis prompts a PLASMIC assessment for TTP. Each of these decisions is better made with the score calculated explicitly than estimated from gestalt.

On inpatient oncology and haematology wards, the ANC is checked daily through the chemotherapy nadir, and the Khorana score is best calculated when systemic therapy is planned, not after a clot has formed. In outpatient clinics, new diagnoses of lymphoma and myeloma are staged with the IPI and ISS or R-ISS at the first visit, because the stage shapes both prognosis discussions and trial eligibility. The Charlson index is most useful in multidisciplinary meetings and pre-treatment assessments, where comorbidity burden needs to be weighed openly rather than sensed vaguely.

For medical students and junior doctors, this library doubles as a structured study companion. Working through the RPI teaches the physiology of the anaemia workup; the 4Ts teaches the clinical reasoning of HIT; and the IPI, ISS and MASCC demonstrate how prognosis systems are constructed from simple clinical variables. Because each calculator page explains its inputs, students learn the score and the reasoning behind it at the same time.

Interpreting results: what the scores change in practice

Every score in this library maps to a decision. A MASCC score of 21 or above supports outpatient management of febrile neutropenia with close follow-up; below 21, admission and intravenous antibiotics are the safer course. A 4Ts score of 0 to 3 makes HIT unlikely and heparin can usually continue, 4 to 5 is intermediate and warrants testing with clinical caution, and 6 to 8 makes HIT likely enough to stop all heparin immediately and start a non-heparin anticoagulant while awaiting laboratory confirmation.

An ANC below 500 defines severe neutropenia and should prompt protective measures and a low threshold for investigating fever; below 100, the risk is profound and isolation precautions are commonly added. A Khorana score of 2 marks intermediate risk and 3 or above high risk, the range in which guidelines discuss pharmacologic thromboprophylaxis for ambulatory patients starting chemotherapy. PESI classes I and II identify low-risk pulmonary embolism where outpatient treatment can be considered, provided social circumstances allow it. The IPI groups patients from low to high risk across its five factors, and the ISS stages myeloma from I to III, each step carrying a meaningfully different expected course that shapes the conversation about treatment goals.

The PLASMIC score deserves special mention because its result changes the urgency of care: a high score in suspected TTP supports starting plasma exchange without delay, since mortality rises steeply when treatment waits for ADAMTS13 results. The Charlson index, by contrast, changes the framing of decisions rather than triggering a single action: a high score is a prompt to discuss goals of care, treatment intensity and supportive care early, not a reason to withhold treatment on its own.

Limitations and pitfalls: what these tools cannot do

Risk scores are derived from specific populations and lose accuracy outside them. The MASCC index was validated in particular febrile neutropenia cohorts and performs less well in patients with hypotension, confusion or organ dysfunction, who should be treated as high risk regardless of the number. The Khorana score applies to ambulatory patients starting chemotherapy; it was not designed for hospitalised patients or those already anticoagulated. The 4Ts score depends on accurate clinical detail, especially the timing of the platelet fall relative to heparin exposure, and incomplete data produces misleading results.

Laboratory timing matters throughout haematology. The ANC is a snapshot that can fall further during the nadir, so a single reassuring value does not end monitoring. The RPI assumes a steady state and is less reliable during acute bleeding or immediately after transfusion. PESI and the revised Geneva score depend on accurate history and vital signs; misrecorded inputs produce confident-looking but wrong outputs. The Charlson index estimates population-level survival and says nothing about an individual patient's resilience or preferences. And prognosis systems such as the IPI predate some modern therapies, so their absolute predictions should be read as orientation rather than prophecy.

Above all, no score overrides clinical instability. A hypotensive, confused patient with febrile neutropenia is high risk whatever the MASCC total; suspected TTP with end-organ ischaemia needs urgent treatment while the PLASMIC score is still being tallied. These calculators sharpen judgement; they do not replace it.

How to use this library

Start from the clinical question, not the tool. If the question is whether this neutropenic fever can be managed at home, open the MASCC calculator; if it is whether heparin is causing this platelet fall, open the 4Ts. Enter values exactly as measured, read the resulting band together with its suggested action, and document the score in the notes so the next clinician sees the reasoning, not just the number. Re-score when the picture changes: counts move, new symptoms appear, and a score calculated yesterday may not describe today's patient. When a result surprises you, trust the surprise and recheck the inputs before acting on it.

Related specialities

These calculators are often used alongside tools from neighbouring fields:

• Infectious Disease
• Nephrology
• Gastroenterology
• Pulmonology

Frequently asked questions